Tau positron emission tomography imaging in C9orf72 repeat expansion carriers.

BACKGROUND AND PURPOSE: AV-1451 (18 F-AV-1451, flortaucipir) positron emission tomography was performed in C9orf72 expansion carriers to assess tau accumulation and disease manifestation. METHODS: Nine clinically characterized C9orf72 expansion carriers and 18 age- and gender- matched cognitively normal individuals were psychometrically evaluated and underwent tau positron emission tomography imaging. The regional AV-1451 standard uptake value ratios from multiple brain regions were analyzed. Spearman correlation was performed to relate the AV-1451 standard uptake value ratio to clinical, psychometric and cerebrospinal fluid measures. RESULTS: C9orf72 expansion carriers had increased AV-1451 binding in the entorhinal cortex compared to controls. Primary age-related tauopathy was observed postmortem in one patient. AV-1451 uptake did not correlate with clinical severity, disease duration, psychometric performance or cerebrospinal fluid markers. CONCLUSION: C9orf72 expansion carriers exhibited increased AV-1451 uptake in entorhinal cortex compared to cognitively normal controls, suggesting a propensity for primary age-related tauopathy. However, AV-1451 accumulation was not associated with psychometric performance in our cohort.

Preclinical trials in autosomal dominant AD: implementation of the DIAN-TU trial.

The Dominantly Inherited Alzheimer's Network Trials Unit (DIAN-TU) was formed to direct the design and management of interventional therapeutic trials of international DIAN and autosomal dominant Alzheimer's disease (ADAD) participants. The goal of the DIAN-TU is to implement safe trials that have the highest likelihood of success while advancing scientific understanding of these diseases and clinical effects of proposed therapies. The DIAN-TU has launched a trial design that leverages the existing infrastructure of the ongoing DIAN observational study, takes advantage of a variety of drug targets, incorporates the latest results of biomarker and cognitive data collected during the observational study, and implements biomarkers measuring Alzheimer's disease (AD) biological processes to improve the efficiency of trial design. The DIAN-TU trial design is unique due to the sophisticated design of multiple drugs, multiple pharmaceutical partners, academics servings as sponsor, geographic distribution of a rare population and intensive safety and biomarker assessments. The implementation of the operational aspects such as home health research delivery, safety magnetic resonance imagings (MRIs) at remote locations, monitoring clinical and cognitive measures, and regulatory management involving multiple pharmaceutical sponsors of the complex DIAN-TU trial are described.

Axonal damage and astrocytosis are biological correlates of grey matter network integrity loss: a cohort study in autosomal dominant Alzheimer disease.

Brain development and maturation leads to grey matter networks that can be measured using magnetic resonance imaging. Network integrity is an indicator of information processing capacity which declines in neurodegenerative disorders such as Alzheimer disease (AD). The biological mechanisms causing this loss of network integrity remain unknown. Cerebrospinal fluid (CSF) protein biomarkers are available for studying diverse pathological mechanisms in humans and can provide insight into decline. We investigated the relationships between 10 CSF proteins and network integrity in mutation carriers (N=219) and noncarriers (N=136) of the Dominantly Inherited Alzheimer Network Observational study. Abnormalities in Aß, Tau, synaptic (SNAP-25, neurogranin) and neuronal calcium-sensor protein (VILIP-1) preceded grey matter network disruptions by several years, while inflammation related (YKL-40) and axonal injury (NfL) abnormalities co-occurred and correlated with network integrity. This suggests that axonal loss and inflammation play a role in structural grey matter network changes. Key points: Abnormal levels of fluid markers for neuronal damage and inflammatory processes in CSF are associated with grey matter network disruptions.The strongest association was with NfL, suggesting that axonal loss may contribute to disrupted network organization as observed in AD.Tracking biomarker trajectories over the disease course, changes in CSF biomarkers generally precede changes in brain networks by several years.

Neuroprotective natural antibodies to assemblies of amyloidogenic peptides decrease with normal aging and advancing Alzheimer's disease.

A number of distinct beta-amyloid (Abeta) variants or multimers have been implicated in Alzheimer's disease (AD), and antibodies recognizing such peptides are in clinical trials. Humans have natural Abeta-specific antibodies, but their diversity, abundance, and function in the general population remain largely unknown. Here, we demonstrate with peptide microarrays the presence of natural antibodies against known toxic Abeta and amyloidogenic non-Abeta species in plasma samples and cerebrospinal fluid of AD patients and healthy controls aged 21-89 years. Antibody reactivity was most prominent against oligomeric assemblies of Abeta and pyroglutamate or oxidized residues, and IgGs specific for oligomeric preparations of Abeta1-42 in particular declined with age and advancing AD. Most individuals showed unexpected antibody reactivities against peptides unique to autosomal dominant forms of dementia (mutant Abeta, ABri, ADan) and IgGs isolated from plasma of AD patients or healthy controls protected primary neurons from Abeta toxicity. Aged vervets showed similar patterns of plasma IgG antibodies against amyloid peptides, and after immunization with Abeta the monkeys developed high titers not only against Abeta peptides but also against ABri and ADan peptides. Our findings support the concept of conformation-specific, cross-reactive antibodies that may protect against amyloidogenic toxic peptides. If a therapeutic benefit of Abeta antibodies can be confirmed in AD patients, stimulating the production of such neuroprotective antibodies or passively administering them to the elderly population may provide a preventive measure toward AD.

Expression of human apolipoprotein E reduces amyloid-beta deposition in a mouse model of Alzheimer's disease.

The epsilon4 allele of apolipoprotein E (apo E) is associated with an increased risk for developing Alzheimer's disease (AD). This may be due to interactions between apo E and the amyloid-beta protein (Abeta). To assess the effects of human apo E isoforms on Abeta deposition in vivo, we bred apo E3 and apo E4 hemizygous (+/-) transgenic mice expressing apo E by astrocytes to mice homozygous (+/+) for a mutant amyloid precursor protein (APPV717F) transgene that develop age-dependent AD neuropathology. All mice were on a mouse apo E null (-/-) background. By nine months of age, APPV717F+/-, apo E-/- mice had developed Abeta deposition, and, as reported previously, the quantity of Abeta deposits was significantly less than that seen in APPV717F+/- mice expressing mouse apo E. In contrast to effects of mouse apo E, similar levels of human apo E3 and apo E4 markedly suppressed early Abeta deposition at nine months of age in APPV717F+/- transgenic mice, even when compared with mice lacking apo E. These findings suggest that human apo E isoforms decrease Abeta aggregation or increase Abeta clearance relative to an environment in which mouse apo E or no apo E is present. The results may have important implications for understanding mechanisms underlying the link between apo E and AD.

Potential role of apoE in structural plasticity in the nervous system; implications for disorders of the central nervous system.

Apolipoprotein E (apoE) is a well characterized 299 amino acid protein that participates in the regulation of plasma cholesterol and lipid metabolism. In humans, apoE has three major protein isoforms: E2 (cys(112), cys(158)); E3 (cys(112), arg(158)); and E4 (arg(112), arg(158)) that are encoded for by a single gene on chromosome 19. Genetic studies have shown that apoE4 is a risk factor for Alzheimer's disease (AD) as well as for poor outcome following certain injuries to the central nervous system (CNS). These genetic data, as well as other data reviewed herein, suggest that apoE may play an important role in the nervous system under certain conditions. This review focuses on studies demonstrating that apoE can modulate neuronal structure and the potential implication of these findings for its role following CNS injury, in AD, and in other neurodegenerative diseases.

Intracerebral grafting of cultured autologous skin fibroblasts into the rat striatum: an assessment of graft size and ultrastructure.

To identify a suitable donor cell population for gene therapy applications to the central nervous system, primary fibroblasts isolated from skin biopsies and maintained in culture are employed as autologous cells for intracerebral grafting within the adult rat striatum. Results from the present investigation reveal that cultured primary skin fibroblasts cease to proliferate once they reach confluence; these cells are thus contact inhibited in vitro. Following implantation within the striatum, the volume of the primary fibroblast grafts, stained immunohistochemically for fibronectin, does not differ significantly at 3 and 8 weeks. The graft size is dependent on the density of the cell suspension, but not dependent on either the number of passages the cells are taken through in culture prior to grafting or on the postoperative survival period. Ultrastructural evidence reveals that at 8 weeks the grafts are composed primarily of collagen and fibroblasts with rough endoplasmic reticulum and vesicles. Reactive astrocytic processes and phagocytic cells are also present in the grafts. The grafts are extensively vascularized with capillaries composed of nonfenestrated endothelium; intercellular junctions are evident at sites of apposition between endothelial cells. It is concluded that primary skin fibroblasts are able to survive for at least 8 weeks following intracerebral implantation and continue to synthesize collagen and fibronectin in vivo. Also, the grafts maintain a constant volume between 3 and 8 weeks, thereby indicating that primary skin fibroblasts do not produce tumors. Finally, dynamic host-to-graft interactions--including phagocytic migration, astrocytic hypertrophy and infiltration within the grafts, and angiogenesis--are features that constitute the structural integration of primary skin fibroblasts grafted within the adult rat central nervous system.

Mechanisms of sprouting in the adult central nervous system: cellular responses in areas of terminal degeneration and reinnervation in the rat hippocampus.

Neurons of the adult mammalian central nervous system are limited in their ability to regenerate in response to injury. In certain circumstances, however, such neurons can exhibit morphological plasticity (e.g. sprouting). Unilateral transection of the perforant path in the adult rat induces terminal degeneration of entorhinal axons within the molecular layer of the ipsilateral hippocampal dentate gyrus. Cholinergic (and other) afferents subsequently sprout within the denervated zone. We show that despite the breach in the blood-brain barrier at the site of the aspirative lesion, the barrier remains intact in the areas of terminal degeneration (and reinnervation), and peripheral monocytic macrophages do not infiltrate this area to participate in the degenerative and/or regenerative events. Perforant path transection does not induce expression of major histocompatibility antigens on reactive cells within the denervated zone, nor are T lymphocytes recruited to this area. T lymphocyte-deficient Nude rats exhibit normal cholinergic sprouting. Perforant path transection does induce rapid and robust proliferation of microglia, and astrocytes to a lesser extent, in areas undergoing terminal degeneration. Histological evaluation after antimitotic administration shows that this glial proliferation is not required for the subsequent neuronal sprouting events. These results show that the reparative process in this model system involves interactions between cells endogenous to the brain in a non-immune context. Knowledge of these cellular responses provides a framework from which to further investigate putative molecular signals involved in initiating the neuronal sprouting events. Discovering the cellular and molecular interactions taking place under sprouting conditions is likely to be critical for understanding the mechanisms of reactive neuronal growth and, furthermore, may provide insights as to why regeneration is so limited in the central nervous system.

Grafting genetically modified cells into the rat brain: characteristics of E. coli beta-galactosidase as a reporter gene.

The utility of grafting genetically modified cells to the mammalian brain was examined using the E. coli beta-galactosidase gene (lacZ) as a reporter gene in retroviral infection. Following implantation of the infected cells to the brain, lacZ continued to be expressed in vivo and could be detected easily with enzyme histochemistry. However, beta-galactosidase-positive cells were also observed in control grafts which had not been infected with the virus. This false-positive staining was found to be endogenous lysosomal activity associated with macrophage infiltration presumably induced by the damage associated with grafting. The E. coli gene product was distinguished from cellular lysosomal beta-galactosidase by using immunohistochemical staining with an antibody specific for E. coli beta-galactosidase. With this antibody, retrovirus-infected cells could be distinguished in the brain, and no false positives were observed in non-infected cells. We conclude that E. coli beta-galactosidase is a useful reporter gene for determining the fate of implanted cells to the brain if appropriate caution is taken to distinguish it from cellular beta-galactosidase by immunocytochemical procedures.

Purification and characterization of astrocyte-secreted apolipoprotein E and J-containing lipoproteins from wild-type and human apoE transgenic mice.

The varepsilon4 allele of apolipoprotein E (apoE) is a genetic risk factor for Alzheimer's disease (AD). In order to gain a better understanding of the molecular mechanisms by which apoE and possibly other apolipoproteins produced in the central nervous system (CNS) influence AD pathogenesis, we have purified and characterized the two most abundant apolipoproteins produced in the CNS, apoE and apoJ. We purified apoE and apoJ from primary cultures of mouse astrocytes, which were derived from transgenic mice expressing human apoE isoforms in the absence of mouse apoE. Utilizing antibody affinity columns, we were able to purify both human apoE3 and apoE4, as well as mouse apoJ-containing lipoproteins. Astrocyte-secreted human apoE was present in high density-like lipoproteins of three predominant sizes ranging from 8 to 15 nm in diameter. Mouse apoJ was in particles between 10 and 17 nm in diameter with a peak size range of approximately 11 nm. ApoE and apoJ were in distinct lipoproteins. Utilization of quick-freeze, deep-etch electron microscopy revealed the apoE particles were discs while the apoJ particles were smaller and more irregular in appearance. The lipid composition of apoE particles was very different from those containing apoJ. ApoE-particles contained a similar mass of apoE and lipid, with cholesterol and phospholipid being about equal in mass per particle. ApoJ-particles were relatively lipid poor (three parts protein, one part lipid), with phospholipids being much more abundant than cholesterol. Detailed characterization of phospholipid composition by electrospray ionization mass spectrometry analysis revealed ethanolamine glycerophospholipids to be the most abundant phospholipid present in both apoE and apoJ particles. Analysis of cerebrospinal fluid from apoE3 and apoE4 transgenic mice revealed that human and mouse apoE were in particles the same size as those secreted by astrocytes. Further use of physiological preparations of CNS-derived lipoproteins may allow for a detailed understanding of the role of these molecules in the normal brain and in diseases such as AD.

Lipoproteins in the central nervous system.

Although the synthesis and metabolism of plasma lipoproteins are well characterized, little is known about lipid delivery and clearance within the central nervous system (CNS). Our work has focused on characterizing the lipoprotein particles present in the cerebrospinal fluid (CSF) and the nascent particles secreted by astrocytes. In addition to carrying lipids, we have found that beta-amyloid (A beta) associates with lipoproteins, including the discoidal particles secreted by cultured astrocytes and the spherical lipoproteins found in CSF. We believe that association with lipoproteins provides a means of transport and clearance for A beta. This process may be further influenced by an interaction between A beta and apoprotein E (apoE), the primary protein component of CNS lipoproteins. Specifically, we have investigated the formation and physiologic relevance of a SDS-stable complex between apoE and A beta. In biochemical assays, native apoE2 and E3 (associated with lipid particles) form an SDS-stable complex with A beta that is 20-fold more abundant than the apoE4:A beta complex. In cell culture, native apoE3 but not E4 prevents A beta-induced neurotoxicity by a mechanism dependent on cell surface apoE receptors. In addition, apoE and the inhibition of apoE receptors prevent A beta-induced astrocyte activation. Therefore, we hypothesize that the protection from A beta-induced neurotoxicity afforded by apoE3 may result from clearance of the peptide by SDS-stable apoE3:A beta complex formation and uptake by apoE receptors.

Astrocyte lipoproteins, effects of apoE on neuronal function, and role of apoE in amyloid-beta deposition in vivo.

The genetic association between the E4 isoform of apolipoprotein E (apoE) and increased risk for Alzheimer's disease (AD) has prompted interest in the neurobiology of apoE and the possible relationship between lipoprotein metabolism in the brain and neurodegenerative disease. ApoE, a product of astrocytes, is abundant in brain and in cerebrospinal fluid (CSF) where it is found in lipoproteins the size of large plasma high-density lipoproteins (HDL). Cultured astrocytes also secrete apoE/HDL, although the lipid and apoprotein composition of these nascent particles differs from that found in CSF, suggesting possible functional differences. In vitro studies have demonstrated isoform-specific effects of apoE on neurite outgrowth, neuronal plasticity, neurotoxicity, lipid peroxidation, oxidative injury, binding to cytoskeletal proteins, and interactions with amyloid-beta (Abeta), a primary component of senile plaques in AD. A number of these proposed functions have also been assessed in apoE -/- mice and transgenic mice expressing human apoE3 or apoE4. Importantly, analysis of transgenic mice overexpressing a mutant form of the human amyloid precursor protein (APP(V717F)) in the presence of mouse apoE, no apoE, or human apoE3 or E4 has demonstrated a critical and isoform-specific role for apoE in neuritic plaque formation, a pathologic hallmark of AD. Together, these data have provided important clues as to possible mechanism(s) by which apoE genotype modifies AD risk.

High density lipoprotein decreases beta-amyloid toxicity in cortical cell culture.

A hallmark of Alzheimer's disease (AD) is the extracellular deposition and accumulation of a 39-43 amino peptide, known as the amyloid beta (A beta) protein, within the brain. It has been postulated that A beta may in some way contribute directly to AD pathogenesis. The epsilon 4 allele of apolipoprotein E (apoE) is a major AD risk factor. Since both apoE and A beta are components of lipoproteins in plasma and cerebrospinal fluid, we asked whether lipoproteins and apoE isoforms would modify the toxicity of A beta (1-42) in cortical cell cultures. We show that high density lipoprotein with or without apoE reduces A beta toxicity and that apoE in the absence of lipoproteins does not affect A beta toxicity. These results suggest that interactions between A beta and lipoproteins in the brain could influence AD pathogenesis.

Learning sets, discrimination reversal, and hippocampal function.

Impairments of discrimination reversal are commonly found following lesions of the hippocampal system. In a recent experiment, however, acquisition of a reversed discrimination was actually facilitated, rather than impaired, by partial lesions of the fimbria-fornix (FFX), an extrinsic fiber connection to the hippocampus. That experiment differed from most previous reversal experiments in that the discriminative stimuli were olfactory rather than spatial or visual, and 3 discriminations were given prior to the reversal of the third discrimination, rather than a single discrimination. The present experiment was designed to determine the generality of the results obtained in the olfactory experiment. Rats with partial lesions of the FFX and operated controls were tested on a series of 3 Go, No-go spatial discriminations, a reversal of the third discrimination, and 4 subsequent discriminations, in that order. Control rats acquired a learning set in the first 3 discriminations, reaching criterion on the third discrimination in fewer trials than they took on the first discrimination. Their choice accuracy was not significantly affected by the reversal and discrimination performance reached an asymptotic level after the reversal. Rats with FFX lesions also acquired a learning set in the first 3 discriminations, but they consistently took longer than control rats to learn each of the 7 discriminations. These rats were especially impaired on the reversal. These results contrast markedly with those obtained when a similar procedure was used with olfactory discriminations. Identification of the variables responsible for these differences should help distinguish those behaviors that require hippocampal function from those that do not.

Effects of brain-derived neurotrophic factor and nerve growth factor on remaining neurons in the lesioned nucleus basalis magnocellularis.

Rats received a unilateral lesion of the nucleus basalis magnocellularis (NBM) by infusion of ibotenic acid. Starting 2 weeks after the lesion, the animals were treated with nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) by intraparenchymal infusion of 3 micrograms per day for 4 weeks. Lesioned control animals received a similar amount of cytochrome c. The activity of choline acetyltransferase (ChAT) in the frontal neocortex was significantly reduced by the lesion (-39%). However, the intraparenchymal treatment with NGF or BDNF did not affect cortical ChAT activity. The number of p75 NGF receptor-immunoreactive neurons in the NBM was significantly decreased (-49%) by the lesion and was not affected by NGF or BDNF. The size of the remaining neurons was significantly increased by NGF (+32%), but not by BDNF (+12%). Similarly, in situ hybridization showed enhanced expression of the p75 NGF receptor following treatment with NGF, but not with BDNF. These results suggest that although BDNF occurs in the target area of cholinergic NBM neurons, its effects on these neurons are less pronounced than those of NGF.

Ventriculo-pulmonary fistula. Case report, literature review and possible surgical approach to the infected LV suture line.

We describe a patient who developed a ventriculo-pulmonary fistula 2 years after resection of a left ventricular aneurysm, and mention the management of two further patients, one with a sinus, the other with a pseudo-aneurysm, both after left ventricular aneurysmectomy, to illustrate a possible surgical approach to a patient with a ventriculo-pulmonary fistula.

Surviving home healthcare: one agency's experience.

Too often, home health agencies are narrow and territorial in their outlook. Ideas need to be sought, developed, and acted upon after all the risks have been weighed. If home health agencies don't manage themselves as businesses, then they will be out of business and not able to serve anyone.

Improving CSF biomarker accuracy in predicting prevalent and incident Alzheimer disease.

OBJECTIVE: To investigate factors, including cognitive and brain reserve, which may independently predict prevalent and incident dementia of the Alzheimer type (DAT) and to determine whether inclusion of identified factors increases the predictive accuracy of the CSF biomarkers Aß(42), tau, ptau(181), tau/Aß(42), and ptau(181)/Aß(42). METHODS: Logistic regression identified variables that predicted prevalent DAT when considered together with each CSF biomarker in a cross-sectional sample of 201 participants with normal cognition and 46 with DAT. The area under the receiver operating characteristic curve (AUC) from the resulting model was compared with the AUC generated using the biomarker alone. In a second sample with normal cognition at baseline and longitudinal data available (n = 213), Cox proportional hazards models identified variables that predicted incident DAT together with each biomarker, and the models' concordance probability estimate (CPE), which was compared to the CPE generated using the biomarker alone. RESULTS: APOE genotype including an ε4 allele, male gender, and smaller normalized whole brain volumes (nWBV) were cross-sectionally associated with DAT when considered together with every biomarker. In the longitudinal sample (mean follow-up = 3.2 years), 14 participants (6.6%) developed DAT. Older age predicted a faster time to DAT in every model, and greater education predicted a slower time in 4 of 5 models. Inclusion of ancillary variables resulted in better cross-sectional prediction of DAT for all biomarkers (p < 0.0021), and better longitudinal prediction for 4 of 5 biomarkers (p < 0.0022). CONCLUSIONS: The predictive accuracy of CSF biomarkers is improved by including age, education, and nWBV in analyses.

Cognitively unimpaired HIV-positive subjects do not have increased 11C-PiB: a case-control study.

OBJECTIVES: Diagnostic challenges exist for differentiating HIV dementia from Alzheimer disease (AD) in older HIV-infected (HIV+) individuals. Similar abnormalities in brain amyloid-beta42 (Alphabeta42) metabolism may be involved in HIV-associated neuropathology and AD. We evaluated the amyloid-binding agent (11)C-Pittsburgh compound B ((11)C-PiB), a biomarker for Alphabeta42 deposition, in cognitively unimpaired HIV+ (n = 10) participants and matched community controls without dementia (n = 20). METHODS: In this case-control study, all participants had an (11)C-PiB scan within 2 years of concomitant CSF studies and neuropsychometric testing. Statistical differences between HIV+ and community controls for demographic and clinical values were assessed by chi(2) tests. Participants were further divided into either low (<500 pg/mL) or normal (>or=500 pg/mL) CSF Alphabeta42 groups with Student t tests performed to determine if regional differences in fibrillar amyloid plaque deposition varied with CSF Alphabeta42. RESULTS: Regardless of CSF Alphabeta42 level, none of the HIV+ participants had fibrillar amyloid plaques as assessed by increased (11)C-PiB mean cortical binding potential (MCBP) or binding potential within 4 cortical regions. In contrast, some community controls with low CSF Alphabeta42 (<500 pg/mL) had high (11)C-PiB MCBP with elevated binding potentials (>0.18 arbitrary units) within cortical regions. CONCLUSIONS: Cognitively unimpaired HIV+ participants, even with low CSF Alphabeta42 (<500 pg/mL), do not have (11)C-PiB parameters suggesting brain fibrillar amyloid deposition. The dissimilarity between unimpaired HIV+ and preclinical AD may reflect differences in Abeta42 production and/or formation of diffuse plaques. Future longitudinal studies of HIV+ participants with low CSF Abeta42 and normal (11)C-PiB are required.