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Positron emission tomography (PET) imaging allows monitoring the progression of amyloid aggregation in the living brain. [ 18 F]-Flortaucipir is the only approved PET tracer compound for the visualisation of tau aggregation. Here, we describe cryo-EM experiments on tau filaments in the presence and absence of flortaucipir. We used tau filaments isolated from the brain of an individual with Alzheimer's disease (AD), and from the brain of an individual with primary age-related tauopathy (PART) with a co-pathology of chronic traumatic encephalopathy (CTE). Unexpectedly, we were unable to visualise additional cryo-EM density for flortaucipir for AD paired helical or straight filaments (PHFs or SFs), but we did observe density for flortaucipir binding to CTE Type I filaments from the case with PART. In the latter, flortaucipir binds in a 1:1 molecular stoichiometry with tau, adjacent to lysine 353 and aspartate 358. By adopting a tilted geometry with respect to the helical axis, the 4.7 Å distance between neighbouring tau monomers is reconciled with the 3.5 Å distance consistent with π-π-stacking between neighbouring molecules of flortaucipir., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 MRC Laboratory of Molecular Biology. Published by Elsevier Ltd.. All rights reserved.)

Our objective was to assess the reported history of seizures in cognitively asymptomatic mutation carriers for autosomal dominant Alzheimer's disease (ADAD) and the predictive value of seizures for mutation carrier status in cognitively asymptomatic first-degree relatives of ADAD patients. Seizure occurrence in the Dominantly Inherited Alzheimer Network observational study was correlated with mutation carrier status in cognitively asymptomatic subjects. Of 276 cognitively asymptomatic individuals, 11 (4%) had experienced seizures, and nine of these carried an ADAD mutation. Thus, in the Dominantly Inherited Alzheimer Network population, seizure frequency in mutation carriers was significantly higher than in noncarriers (p = 0.04), and the positive predictive value of seizures for the presence of a pathogenic mutation was 81.8%. Among cognitively asymptomatic ADAD family members, the occurrence of seizures increases the a priori risk of 50% mutation-positive status to about 80%. This finding suggests that ADAD mutations increase the risk of seizures., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Among genetically determined neurodegenerative diseases, the dominantly inherited prion protein cerebral amyloidoses are characterized by deposition of amyloid in cerebral parenchyma or blood vessels. Among them, Gerstmann-Sträussler-Scheinker disease has been the first to be described. Their clinical, neuropathologic, and molecular phenotypes are distinct from those observed in Creutzfeldt-Jakob disease (CJD) and related spongiform encephalopathies. It is not understood why specific mutations in the prion protein gene (PRNP) cause cerebral amyloidosis and others cause CJD. A significant neurobiologic event in these amyloidoses is the frequent coexistence of prion amyloid with tau neurofibrillary pathology, a phenomenon suggesting that similar pathogenetic mechanisms may be shared among different diseases in the sequence of events occurring in the cascade from amyloid formation to tau aggregation. This chapter describes the clinical, neuropathologic, and biochemical phenotypes associated with each of the PRNP mutations causing an inherited cerebral amyloidosis and emphasizes the variability of phenotypes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Familial British dementia (FBD) and familial Danish dementia (FDD) are caused by mutations in the BRI 2 gene. These diseases are characterized clinically by progressive dementia and ataxia and neuropathologically by amyloid deposits and neurofibrillary tangles. Herein, we investigate BRI 2 protein accumulation in FBD, FDD, Alzheimer disease and Gerstmann-Sträussler-Scheinker disease. In FBD and FDD, we observed reduced processing of the mutant BRI 2 pro-protein, which was found accumulating intracellularly in the Golgi of neurons and glial cells. In addition, we observed an accumulation of a mature form of BRI 2 protein in dystrophic neurites, surrounding amyloid cores. Accumulation of BRI 2 was also observed in dystrophic neurites of Alzheimer disease and Gerstmann-Sträussler-Scheinker disease cases. Although it remains to be determined whether intracellular accumulation of BRI 2 may lead to cell damage in these degenerative diseases, our study provides new insights into the role of mutant BRI 2 in the pathogenesis of FBD and FDD and implicates BRI 2 as a potential indicator of neuritic damage in diseases characterized by cerebral amyloid deposition., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In the present study we aimed to determine the prevalence of C9ORF72 GGGGCC hexanucleotide expansion in our cohort of 53 frontotemporal lobar degeneration (FTLD) patients and 174 neurologically normal controls. We identified the hexanucleotide repeat, in the pathogenic range, in 4 (2 bv-frontotemporal dementia (FTD) and 2 FTD-amyotrophic lateral sclerosis [ALS]) out of 53 patients and 1 neurologically normal control. Interestingly, 2 of the C9ORF72 expansion carriers also carried 2 novel missense mutations in GRN (Y294C) and in PSEN-2(I146V). Further, 1 of the C9ORF72 expansion carriers, for whom pathology was available, showed amyloid plaques and tangles in addition to TAR (trans-activation response) DNA-binding protein (TDP)-43 pathology. In summary, our findings suggest that the hexanucleotide expansion is probably associated with ALS, FTD, or FTD-ALS and occasional comorbid conditions such as Alzheimer's disease. These findings are novel and need to be cautiously interpreted and most importantly replicated in larger numbers of samples., (Published by Elsevier Inc.)

The vertical transmission of a prion disease from infected mothers to their offspring is believed to be one of the routes for the natural spread of animal prion diseases. Supporting this notion is the observation that prion infectivity occurs in the placenta of infected ewes. Furthermore, the prion protein (PrP), both in its cellular form (PrP(C)) and its pathological isoform (PrP(Sc)), has been observed at the fetal-maternal interface of scrapie-infected sheep. However, whether these features of prion infectivity also hold true for human prion diseases is currently unknown. To begin to address such an important question, we examined PrP in the uterus as well as gestational tissues, including the placenta and amniotic fluid, in a pregnant woman with sporadic Creutzfeldt-Jakob disease (CJD). Although the proteinase K (PK)-resistant prion protein, PrP27-30, was present in the brain tissues of the mother, the PrP detected in the uterus, placenta, and amniotic fluid was sensitive to PK digestion. Unlike PrP(C) in the brain and adjacent cerebrospinal fluid, the predominant PrP species in the reproductive and gestational tissues were N-terminally truncated, similar to urine PrP. Our study did not detect abnormal PrP in the reproductive and gestational tissues in this case of CJD. Nevertheless, examination by a highly sensitive bioassay is ongoing to ascertain possible prion infectivity from CJD in the amniotic fluid.

Recent evidence has suggested that truncation of tau protein at the caspase cleavage site D421 precedes hyperphosphorylation and may be necessary for the assembly of tau into filaments in Alzheimer's disease and other tauopathies. Here we have investigated the time course of the appearance of phosphorylated and truncated tau in the brain and spinal cord of mice transgenic for mutant human P301S tau protein. This mouse line recapitulates the essential molecular and cellular features of the human tauopathies, including tau hyperphosphorylation, tau filament formation, and neurodegeneration. Soluble tau was strongly phosphorylated at 1 to 6 months of age. Low levels of phosphorylated, sarkosyl-insoluble tau were detected at 2 months, with a steady increase up to 6 months of age. Tau truncated at D421 was detected at low levels in Tris-soluble and detergent-soluble tau at 3 to 6 months of age. By immunoblotting, it was not detected in sarkosyl-insoluble tau. However, by immunoelectron microscopy, a small percentage of tau in filaments from brain and spinal cord of transgenic mice was truncated at D421. Similar findings were obtained using dispersed filaments from Alzheimer's disease and FTDP-17 brains. The late appearance and low abundance of tau ending at D421 indicate that it is unlikely that truncation at this site is necessary for the assembly of tau into filaments.

Non-Alzheimer's disease of the frontal type, or frontotemporal dementia (FTD), is the second most common form of dementia. Yet, a detailed characterization of the disease has been especially limiting. To identify mechanisms possibly involved in disease pathology or progression, a proteomic analysis of proteins isolated from human frontal cortex with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) was performed. We used 2D gel electrophoresis and MALDI-TOF to identify a total of 24 proteins differentially expressed in FTDP-17. We identified a ubiquitin C-terminal hydrolase, UCHL1, as well as several proteins involved in oxidative stress to be differentially expressed. Data presented implicate UCHL1 and ubiquitin-mediated degradation as well as oxidative stress response in disease pathology or progression.

Recent evidence has suggested that an abnormal reactivation of the cell cycle may precede and cause the hyperphosphorylation and filament formation of tau protein in Alzheimer's disease and other tauopathies. Here we have analyzed the expression and/or activation of proteins involved in cell-cycle progression in the brain and spinal cord of mice transgenic for mutant human P301S tau protein. This mouse line recapitulates the essential molecular and cellular features of the human tauopathies, including hyperphosphorylation and filament formation of tau protein. None of the activators and co-activators of the cell cycle tested were overexpressed or activated in 5-month-old transgenic mice when compared to controls. By contrast, the levels of cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1 were increased in brain and spinal cord of transgenic mice. Both inhibitors accumulated in the cytoplasm of nerve cells, the majority of which contained inclusions made of hyperphosphorylated tau protein. A similar staining pattern for p21Cip1 and p27Kip1 was also present in the frontal cortex from a case of FTDP-17 with the P301L tau mutation. Thus, reactivation of the cell cycle was not involved in tau hyperphos-phorylation and filament formation, consistent with expression of p21Cip1 and p27Kip1 in tangle-bearing nerve cells.

The clinical and neuropathological features in the P301L tauopathy have been described in several kindreds. In this study, we present findings in two previously unreported patients, evaluated both genetically, neuropathologically, and with multiparametric confocal immunofluorescence. The patients were female, with age 65 and 75 years old, respectively. Both exhibited clinical symptoms of frontotemporal dementia (FTD). Marked atrophy of the frontal and temporal lobes with moderate atrophy of the remaining cerebral and brain stem structures was present. The substantia nigra was pale. The atrophic neocortical regions exhibited neuronal loss, marked gliosis, status spongiosus, and occasional ballooned neurons. By light microscopy, the most striking findings were argyrophilic perinuclear rings, frequently with an attached small inclusion (mini Pick-like body), especially prominent in dentate granule cells, entorhinal and temporal cortices, and to a lesser extent in CA1. These structures were immunopositive for tau protein (Tau-2, AT-8, PHF-1, MC-1). Numerous astrocytic plaques, tuft-shaped astrocytes, coiled bodies, and dystrophic neurites were also present. Confocal immunofluorescence with a P301L-specific antibody directly demonstrated the presence of the mutated protein in the PHF-1 positive aggregates. The mutated tau protein (4-repeat tau) was detected in the mini Pick-like bodies, indicating an important biochemical difference between these inclusions and classical Pick bodies (3-repeat tau). Additionally, since 4-repeat tau protein is not normally present in dentate granule cells, this result also suggests an abnormality in the mRNA splicing mechanisms. The structural features of the involvement of proteolytic systems in this tauopathy were assessed by immunohistochemistry for the active form of calpain II (C-27) and ubiquitin. Colocalization of PHF-1 positive aggregates with C-27 points to the possible involvement of calpain in tau protein hyperphosphorylation. Absence of immunostaining for ubiquitin indicates possible dysfunction of the ubiquitin-proteasome system in this tauopathy.

Background: The aggregation of specific proteins is a common feature of the familial dementias, but whether the formation of neuronal inclusion bodies is a causative or incidental factor in the disease is not known. To clarify this issue, we investigated five families with typical neuroserpin inclusion bodies but with various neurological manifestations., Methods: Five families with neurodegenerative disease and typical neuronal inclusions had biopsy or autopsy material available for further examination. Immunostaining confirmed that the inclusions were formed of neuroserpin aggregates, and the responsible mutations in neuroserpin were identified by sequencing of the neuroserpin gene (SERPINI1) in DNA from blood samples or from extraction of histology specimens. Molecular modelling techniques were used to predict the effect of the gene mutations on three-dimensional protein structure. Brain sections were stained and the topographic distribution of the neuroserpin inclusions plotted., Findings: Each of the families was heterozygous for an amino acid substitution that affected the conformational stability of neuroserpin. The least disruptive of these mutations (S49P), as predicted by molecular modelling, resulted in dementia after age 45 years, and presence of neuroserpin inclusions in only a few neurons. By contrast, the most severely disruptive mutation (G392E) resulted, at age 13 years, in progressive myoclonus epilepsy, with many inclusions present in almost all neurons., Interpretation: The findings provide evidence that inclusion-body formation is in itself a sufficient cause of neurodegeneration, and that the onset and severity of the disease is associated with the rate and magnitude of neuronal protein aggregation.

Gerstmann-Sträussler-Scheinker disease (GSS) is characterized by the accumulation of proteinase K (PK)-resistant prion protein fragments (PrP(sc)) of approximately 7 to 15 kd in the brain. Purified GSS amyloid is composed primarily of approximately 7-kd PrP peptides, whose N terminus corresponds to residues W(81) and G(88) to G(90) in patients with the A117V mutation and to residue W(81) in patients with the F198S mutation. The aim of this study was to characterize PrP in brain extracts, microsomal preparations, and purified fractions from A117V patients and to determine the N terminus of PrP(sc) species in both GSS A117V and F198S. In all GSS A117V patients, the approximately 7-kd PrP(sc) fragment isolated from nondigested and PK-digested samples had the major N terminus at residue G(88) and G(90), respectively. Conversely, in all patients with GSS F198S, an approximately 8-kd PrP(sc) fragment was isolated having the major N terminus start at residue G(74). It is possible that a further degradation of this fragment generates the amyloid subunit starting at W(81). The finding that patients with GSS A117V and F198S accumulate PrP(sc) fragments of different size and N-terminal sequence, suggests that these mutations generate two distinct PrP conformers.

Neuroserpin isolated from inclusion bodies in the brain of a patient with a neurodegenerative disease was characterized biochemically. The protein consisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was heterogeneous ending at residues 405, 407, 409, and 410. Arg was present at position 52. No normal Ser52 was found indicating that only mutant neuroserpin was present in the inclusion bodies. The three potential Asn glycosylation sites all contained carbohydrate. DNA sequence analysis of exons 2 to 9 of the neuroserpin gene in the proband showed the published normal neuroserpin sequence except for the presence of both adenine and cytosine at the first position of codon 52, that indicates heterozygosity for both the normal Ser(AGT) and variant Arg(CGT) at this position in the expressed protein. Restriction fragment length polymorphism analysis of a polymerase chain reaction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls were negative. Chemical characterization of the variant neuroserpin will significantly enhance the understanding of this protein in both normal physiology and neurodegenerative diseases.

A missense mutation in the gene coding for the G-protein-activated inwardly rectifying potassium (GIRK) channel, GIRK2, is responsible for apoptosis in the external germinal layer (EGL) of the cerebellum and a nonapoptotic death of midbrain dopaminergic neurons in the weaver (wv) mouse. Failure of axonogenesis and migration are considered to be the primary consequences of GIRK2 channel malfunction in the cerebellum. We investigated whether a disruption of the cell cycle precedes the failure of migration and axonogenesis and leads to massive apoptosis. To this end, immunohistochemistry and immunoblotting for PCNA, Cdk4, cyclin D, cyclin A, and the Cdk inhibitor p27/kip1, as well as in situ end-labeling for apoptotic DNA fragmentation, were applied to cerebella of P7-P21+/+, wv/+, and wv/wv mice. In +/+ and wv/+ mice, the expression of cell cycle proteins was limited to the outer, premigratory zone of the EGL. Antibodies to p27, a marker of cell differentiation, gave a reverse staining pattern. Due to migration delay, patches of p27-positive cells persisted in the outer EGL in P21 wv/+ mice. On the contrary, marked cell cycle up-regulation and absence of p27 occurred throughout the EGL at all ages in wv/wv mice, indicating an inability to switch off the cell cycle. Mitotic index evaluation showed that cell cycle activation was unrelated to proliferative events. Cell cycle proteins were not expressed in the substantia nigra, suggesting that nonapoptotic death of mature dopaminergic neurons is not preceded by abortive cell cycle re-entry. Our data show that abnormalities of the cell cycle in wv/wv cerebellum represent a major and early consequence of GIRK2 channel malfunction and may strongly influence the susceptibility of EGL cells to apoptosis. These observations may help in understanding the pathogenesis of human neurological channelopathies.

We have investigated the proteolytic cleavage of the cellular (PrPC) and pathological (PrPSc) isoforms of the human prion protein (PrP) in normal and prion-affected brains and in tonsils and platelets from neurologically intact individuals. The various PrP species were resolved after deglycosylation according to their electrophoretic mobility, immunoreactivity, Sarkosyl solubility, and, as a novel approach, resistance to endogenous proteases. First, our data show that PrPC proteolysis in brain originates amino-truncated peptides of 21 to 22 and 18 (C1) kd that are similar in different regions and are not modified by the PrP codon 129 genotype, a polymorphism that affects the expression of prion disorders. Second, this proteolytic cleavage of PrPC in brain is blocked by inhibitors of metalloproteases. Third, differences in PrPC proteolysis, and probably in Asn glycosylation and glycosylphosphatidylinositol anchor composition, exist between neural and non-neural tissues. Fourth, protease-resistant PrPSc cores in sporadic Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker F198S disease brains all have an intact C1 cleavage site (Met111-His112), which precludes disruption of a domain associated with toxicity and fibrillogenesis. Fifth, the profile of endogenous proteolytic PrPSc peptides is characteristic of each disorder studied, thus permitting the molecular classification of these prion diseases without the use of proteinase K and even a recognition of PrPSc heterogeneity within type 2 CJD patients having different codon 129 genotype and neuropathological phenotype. This does not exclude the role of additional factors in phenotypic expression; in particular, differences in glycosylation that may be especially relevant in the new variant CJD. Proteolytic processing of PrP may play an important role in the neurotropism and phenotypic expression of prion diseases, but it does not appear to participate in disease susceptibility.

Missense mutations in the alpha-synuclein gene cause familial Parkinson's disease (PD), and alpha-synuclein is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB variant of Alzheimer's disease (AD). To determine whether alpha-synuclein is a component of LBs in familial AD (FAD) patients with known mutations in presenilin (n = 65) or amyloid precursor protein (n = 9) genes, studies were conducted with antibodies to alpha-, beta-, and gamma-synuclein. LBs were detected with alpha- but not beta- or gamma-synuclein antibodies in 22% of FAD brains, and alpha-synuclein-positive LBs were most numerous in amygdala where some LBs co-localized with tau-positive neurofibrillary tangles. As 12 (63%) of 19 FAD amygdala samples contained alpha-synuclein-positive LBs, these inclusions may be more common in FAD brains than previously reported. Furthermore, alpha-synuclein antibodies decorated LB filaments by immunoelectron microscopy, and Western blots revealed that the solubility of alpha-synuclein was reduced compared with control brains. The presence of alpha-synuclein-positive LBs was not associated with any specific FAD mutation. These studies suggest that insoluble alpha-synuclein aggregates into filaments that form LBs in many FAD patients, and we speculate that these inclusions may compromise the function and/or viability of affected neurons in the FAD brain.

Antibodies to the prion protein (PrP) have been critical to the neuropathological and biochemical characterization of PrP-related degenerative diseases in humans and animals. Although PrP is highly conserved evolutionarily, there is some sequence divergence among species; as a consequence, anti-PrP antibodies have a wide spectrum of reactivity (from strong immunopositivity to lack of reactivity) when challenged with PrP from diverse species. We have produced an antibody (anti-PrP95-108) raised against a synthetic peptide corresponding to residues 95 to 108 of human PrP and have characterized it by epitope mapping, Western immunoblot analysis, and immunohistochemistry. The antibody recognizes not only human PrP isoforms but also pathological PrP from all species tested (ie, cattle, sheep, hamsters, and mice). This is probably due to the fact that the epitope recognized by this antibody includes residues 100 to 108 of human PrP, a sequence that is also present in PrP of several other species. Thus, this reagent is valuable not only for the study of human prion diseases but also for analysis of the possible relationship between human and animal disorders.

Neuronal death affects selectively granule cell precursors of the cerebellum and the dopaminergic neurons of midbrain in the weaver mutant mouse. The weaver phenotype is associated with a missense mutation in the gene coding for the GIRK2 potassium channel, which results in chronic depolarization. Using DNA gel electrophoresis, electron microscopy (EM), the in situ end-labeling (ISEL) technique at the light and EM level, and immunohistochemistry for apoptosis-related proteins c-Jun and proliferating cell nuclear antigen (PCNA), we have investigated the mechanisms of cell death in cerebellum and substantia nigra. Between postnatal day P1 and P21, in the external germinal layer of the cerebellum, most degenerating granule cell precursors were found to aggregate to form clusters. Degenerating cells exhibited strong nuclear staining for ISEL, c-Jun, and PCNA and had a typical apoptotic morphology by EM. Increased c-Jun and ISEL staining were also occasionally seen in Purkinje cells. Between P14 and P21, when dopaminergic neurons start to degenerate, staining for ISEL, c-Jun, and PCNA in weaver substantia nigra was the same as in controls. By EM, however, we found only in weaver mice numerous dopaminergic cells that showed extensive vacuolar and autophagic changes of cytoplasm, preservation of membrane and organelle integrity, and absence of chromatin condensation or DNA fragmentation by EM-ISEL. The combination of vacuolar and autophagic changes identifies a novel type of non-necrotic, nonapoptotic cell death. After biochemical analysis of DNA, a clear-cut laddering, suggestive of oligonucleosomal fragmentation, was present in samples from weaver cerebellum. Cell death diversity appears to be influenced by specific features of target cells. These findings may be relevant for understanding the mechanisms of cell death in neurodegenerative diseases.

Prion diseases are neurodegenerative disorders characterized by the accumulation of abnormal isoforms of prion protein (PrPSc) in the central nervous system. PrPSc isoforms differ from their normal homologue (PrPC), in that they possess increased beta-sheet conformation, are partially protease resistant and may be associated with amyloid deposition. Amyloid proteins are thought to derive from soluble precursors or fragments thereof, present in biological fluids, which in the disease state undergo conformational change leading to aggregation and deposition in target tissues. We report here that platelets carry PrP mRNA and release PrPC, a sialoglycoprotein bound to the cell surface by a glycosylphosphatidylinositol (GPI) anchor. Soluble PrPC, and a N-terminal truncated PrPC isoform starting at position 90 are secreted by resting and agonist-stimulated platelets and are detectable after partial deglycosylation of releasates. N-terminal sequence analysis of the soluble 27-30 kDa isoform, GQGGGTHSQ(W)NKP, revealed homology to scrapie PrP27-30, the protease resistant core derived from PrPSc. These findings indicate that in addition to PrPC, platelets process a soluble PrP27-30 isoform. Whether this isoform can be converted in scrapie PrP27-30 remains to be determined.

Amyloid fibrils were isolated from the brain tissue of two individuals who died with familial Alzheimer's disease, one with the phenylalanine 717 mutation in amyloid precursor protein (APP) and one with the isoleucine 717 APP mutation. After solubilization in guanidine hydrochloride and fractionation by sieve chromatography, low molecular weight fractions were treated with cyanogen bromide to generate the beta-peptide fragment starting after the methionine at position 35. Amino acid sequence analysis of all resultant peptides identified the peptide Val-Gly-Gly-Val-Val-Ile-Ala which represents residues 36-42 of the beta-amyloid peptide. No sequence beyond position 42 was found. These findings show that the amino acid substitution at position 717 is not incorporated into the amyloid deposits and suggests that the mutation may have metabolic affects which determine pathogenesis.

In Alzheimer's disease, deposits of amyloid beta-protein are apparently derived from intracellular processing of a large precursor protein. We have measured concentrations of this precursor in cerebrospinal fluid (CSF) from six members of a family affected by presenile Alzheimer's disease associated with a point mutation of the precursor gene. One gene carrier with clinical signs of the disorder had low CSF concentrations of the precursor, similar to those of three patients with sporadic Alzheimer's disease subsequently confirmed at necropsy. Two symptom-free gene carriers had CSF precursor concentrations similar to those of non-demented controls, though the value was lower in one, who had deficits revealed on neuropsychological testing, than in the other. These findings suggest that low concentrations of soluble amyloid precursor proteins in the CSF reflect the process that results in amyloid plaque formation and vascular deposition in Alzheimer's disease.

The injection of aluminum powder into the cerebrospinal fluid of adult rabbits induced a slowly progressing encephalomyelopathy characterized at first by alteration of posture and then by myoclonic jerks and muscle weakness. Neurofibrillary degeneration was the hallmark of the disease and involved most of the gray areas. Giant axonal swellings were also numerous, particularly in the proximal axonal segment of neurons of the anterior horns. In the anterior horns the number of neurons with neurofibrillary degeneration decreased with time, while the images of neuronophagia increased in number in the rabbits killed in the second and third month after aluminum injection. In these animals there were also pathologic changes in the peripheral nerves and muscles. The peripheral nerve showed wallerian-like degeneration. Furthermore, in some animals, the presence of nodal axonal swellings and of paranodal myelin retraction were expression also of a distal axonopathy. Neurogenic muscular atrophy appeared in animals sacrificed in the second and third month after injection.

Neurofibrillary (neurofilament) tangles were induced in cultured neurons of newborn mouse dorsal root ganglia by exposure to maytanprine, an anti-microtubule drug. By 12-24 h of treatment, small short neurofilament bundles were found in the neuronal perikarya and proximal portions of the neurites. By 48-72 h of treatment, small neurofilament bundles were assembled into larger masses, and after 72 h and onward several neurofilament bundles coalesced into single large distinctive perinuclear rings in the neuronal perikarya. A histometric analysis of maytanprine treated axons demonstrated that the density of microtubules decreased rapidly, while that of neurofilaments decreased more slowly. As a result of microtubule depolymerization by maytanprine treatment, neurofilaments change their distribution pattern in neuronal perikarya and subsequently form tangles.