Aluminium and the pathogenesis of Alzheimer's disease: a summary of evidence

Known risk factors for Alzheimer's disease (AD) are few and insufficient knowledge is available to recommend steps to reduce AD in our ageing populations. Although not 'the cause', considerable evidence implicates human ingestion of aluminium as a possible risk factor for the expression of dementia of the Alzheimer type. A recent epidemiological study in Ontario relating the incidence of AD to aluminium in drinking water strongly supports this conclusion. To test further the hypothesis that aluminium may play a role in the pathogenesis of AD we conducted a clinical trial employing the trivalent metal ion binding compound, desferrioxamine. The design was a two-year randomized trial with behavioural assessments blinded to study assignment. Sixty-three patients with probable AD were selected who were living at home and were under 74 years. Forty-eight signed an informed consent and completed all initial testing. The main outcome measure was a video-recorded home-behavioural assessment of measures of skills of daily living. The principal outcome was that the mean slope for performance of the skills of daily living for the group without treatment was -1.72% maximum score/month, compared to -0.87% maximum score/month for the group treated with desferrioxamine (P = 0.038). Considerable evidence supports the hypothesis that aluminium has an active role in the pathogenesis of AD.

Ligand specific effects on aluminum incorporation and toxicity in neurons and astrocytes

Aluminum is present in many manufactured foods and medicines and is added to drinking water for purification purposes. It has been proposed that aluminum is a contributing factors to several neurodegenerative disorders such as Alzheimer's disease. However, this remains controversial primarily due to the unusual properties of aluminum and a lack of information on its cellular sites of action. To resolve some of these questions, we have examined aluminum uptake in both neuronal and astroglial cells as well as the role of metal speciation. The relative accumulation of four aluminum salts, aluminum maltolate, aluminum lactate, aluminum chloride and aluminum fluoride, was investigated and correlated with cell viability and intracellular distribution as determined by morin staining. Significant differences in aluminum incorporation and toxicity were observed in both neuronal and glia cells with the largest effects exhibited by the maltol species. This was accompanied by a nuclear accumulation in the neuronal cell line that was contrasted by the perinuclear, vesicular distribution in astrocytes that partially co-localized with cathepsin D, a lysosomal marker. These findings demonstrate differences in aluminum species and highlights the importance of these factors in modulating the toxic effect of aluminum.

Resolution of allelic and non-allelic variants of histone H1 by cation-exchange-hydrophilic-interaction chromatography

A mixed-mode high-performance liquid chromatography (HPLC) method that resolves the six known non-allelic variants of chicken erythrocyte histone H1 is described. Common, but previously unknown, allelic variants of H1 that comigrate in polyacrylamide gel electrophoresis are also resolved. The resolution of H1 variants achieved by this method should be useful in determining the functional significance of H1 sequence heterogeneity and in analyses of post-translational modification of H1. Furthermore, the principles behind the separation should be applicable to analyses of polymorphism in other proteins.

Capillary electrophoresis of histone H1 variants at neutral pH in dynamically modified fused- silica tubing

Existing methods for the analysis of histone H1 by capillary electrophoresis (CE) employ acidic buffers (pH <3.0) to suppress silanol ionization and minimize the loss of these extremely basic proteins by adsorption to capillary walls. Here we describe the use of Polybrene (PB) as a dynamic modification reagent in a simple procedure that facilitates the analysis of chicken H1 at neutral pH. PB is adsorbed to the inner surfaces of capillaries to render them cationic prior to use and a low concentration of PB is included in the electrolyte to replenish the coating during use. Inclusion of ethylenediaminetetraacetic acid (EDTA) in the electrolyte results in the assembly of a dynamic cation-exchange layer upon the immobilized PB that influences the relative mobilities of H1 variants. The six nonallelic variants of H1 known in this species as well as certain allelic variants are resolved. Because the procedure is effective in preventing the adsorption of proteins as basic as H1 at neutral pH, this strategy should facilitate CE analyses of many basic proteins under conditions that maintain their native conformation.

Run-on gene transcription in human neocortical nuclei. Inhibition by nanomolar aluminum and implications for neurodegenerative disease

The incorporation of [alpha-32P]-uridine triphosphate into DNA transcription products was examined in short post-mortem interval (PMI) human brain neocortical nuclei (n, 22; PMI, 0.5-24 h) using run-on-gene transcription. Reverse Northern dot-blot hybridization of newly synthesized RNA against either total cDNA or Alu repetitive DNA indicated that human brain neocortical nuclei of up to 4-h PMI were efficient in incorporating radiolabel into new transcription products, after which there was a graded decline in de novo RNA biosynthetic capacity. To test the effects of 0-3000 nM concentrations of ambient aluminum on RNA polymerase I (RNAP I) and RNA polymerase II (RNAP II) transcription, dot blots containing 0.5, 1.0, 2.0, and 5.0 micrograms of DNA for (1) the human-specific Alu repetitive element (2) the neurofilament light (NFL) chain, and (3) glial fibrillary acidic protein (GFAP) were Northern hybridized against newly synthesized radiolabeled total RNA. These DNAs represent heterogeneous nuclear RNA (hnRNA), neuronal-, and glial-specific markers, respectively. We report here a dose-dependent repression in the biosynthetic capabilities of brain RNAP II in the range of 50-100 nM aluminum, deficits similar to those previously described using a rabbit neocortical nuclei transcription system and at concentrations that have been reported in Alzheimer's disease (AD) euchromatin. Transcription from RNAP II and the neuron-specific NFL gene in the presence of aluminum was found to be particularly affected. These findings support the hypothesis that brain gene transcription in the presence of trace amounts of ambient aluminum impairs mammalian brain DNA to adequately read out genetic information.

Can the controversy of the role of aluminum in Alzheimer's disease be resolved? What are the suggested approaches to this controversy and methodological issues to be considered?

Aluminum (Al) is unquestionably neurotoxic in both experimental animals and certain human diseases. Minute quantities injected intracerebrally into rabbits will induce severe neurological symptoms and neuropathological features of neurodegeneration. Hyper-aluminemia often develops in patients with renal failure being treated with intermittent hemodialysis on a chronic basis, and in severe cases results in an encephalopathy. Uremic adults and premature infants not on dialysis treatment also can develop encephalopathy due to Al toxicity, as is the case when large amounts of alum are used as a urinary bladder irrigant. There are many other examples of Al-induced neurotoxicity; however, the question as to whether Al presents a health hazard to humans as a contributing factor to Alzheimer's disease is still the subject of debate. Several lines of evidence are presented that have formed the basis of the debate concerning the possible pathogenic role for Al in Alzheimer's disease. Important evidence for an Al-Alzheimer's causal relationship is the observation by laser microprobe mass analysis (LMMS) of the presence of Al in neurofibrillary tangles, although there are conflicting data on the extent of the Al deposition. The relatively poor sensitivity of some of the analytical instruments available for these challenging in situ microanalyses could explain the discrepant results, although LMMS and perhaps secondary ion mass spectrometry (SIMS) appear to be sufficiently sensitive. Harmonization of the techniques is an essential next step. There is new evidence that exposure to Al from drinking water might result in cognitive impairment and an increased incidence of Alzheimer's disease. However, these epidemiological studies have inherent problems that must be scrutinized to determine if an association really does exist. An understanding of a possible enhanced bioavailability of Al in this type of exposure, versus other exposures such as antacid intake or industrial exposure, needs to be considered and explored. There has been one promising clinical trial of the treatment of Alzheimer's disease patients with the Al chelator desferrioxamine (DFO). Further studies are needed, and if confirmation is forthcoming then such data could also support an Al-Alzheimer's disease link as well as suggesting that DFO offers potential as a therapeutic agent. The possibility that iron might be the offending agent needs to be considered since DFO is a very strong iron chelator. The significance of Al-induced neurofibrillary degeneration in experimental animals should be assessed especially in light of new data showing that this model exhibits abnormally phosphorylated tau protein structures in the neuronal perikarya. Thus the key questions that must be answered before it can be asserted that Al possesses causal relationship to Alzheimer's disease, are as follows and are addressed in this present discussion: (1) Are there elevations of the concentration of Al in the brains of Alzheimer's disease patients? (2) Is there a relationship between environmental exposure to Al, particularly in drinking water, and an increased risk of Alzheimer's disease? (3) Is treatment with DFO a potentially useful therapeutic approach and to what extent might beneficial effects of DFO implicate Al in the etiology of Alzheimer's disease? (4) Are there similarities between the experimental animal studies and Alzheimer's disease particularly in the development of abnormal forms of tau seen in neurofibrillary tangles? (5) Does Al promote the deposition of the A beta peptide in Alzheimer's disease? (6) Does hyperaluminemia associated with long-term hemodialysis treatment induce neurofibrillary degeneration? If the answer to each of these six questions is yes, then does this assert that Al possesses a causal relationship to Alzheimer's disease? On the other hand, must all six be met to be able to make this assertion?

Further thoughts on the aluminum-Alzheimer's disease link

STUDY OBJECTIVE AND METHOD: The results of studies on aluminum (Al) and Alzheimer's disease (AD) from groups in Newcastle, UK and Ontario, Canada were compared in order to explain why the former were unable to detect a link while the latter could, and to suggest alternative ways of examining the data.

RESULTS

The Al concentrations in the Newcastle study were relatively small compared with the Ontario ones. When Al concentrations > 250 micrograms/l were used, the RRs were greater for AD than for other forms of dementia, and the RRs were lower for those under 75 years and greater at ages 85 years and over than at ages above 75 years. The relationship between dementia and Al concentrations was U or J shaped--there was a minimum at an Al concentration of 100 micrograms/l. Other constituents or properties such as silicic acid, fluoride, turbidity, iron, and pH all have an effect on the relationship.

CONCLUSIONS

Analyses of the type reported from Newcastle can yield further information if they are extended to include multivariate analyses that take account of other water constituents which can affect the relationship between Al water concentrations and AD are carried out. The relationship between Al and dementia may be U or J shaped rather than linear. With regard to AD, the group aged less than 65 years is not the best one in which to explore a relationship. Lastly, it may be that a link with AD is most meaningful at relatively high Al water concentrations.

Sensitive detection of metallothioneins-1, -2 and -3 in tissue homogenates by immunoblotting: a method for enhanced membrane transfer and retention

Standard immunoblotting procedures were unable to detect metallothioneins-1 and 2 (MT-1, MT-2) and metallothionein-3 (MT-3)/growth inhibitory factor (GIF) in unfractionated brain homogenates. We have developed a novel process which involves the inclusion of 2 mM CaCl2 in electrophoretic transfer buffers and glutaraldehyde fixation following transfer to either nitrocellulose or polyvinylidene difluoride (PVDF) membranes. Using commercial MT antibodies and a specific MT-3 polyclonal antibody raised in our laboratory, we have been able to detect all three MTs on both membrane types with a detection limit of approx. 10 ng for MT-1 and MT-2. Nitrocellulose membrane pore size had no noticeable effect on detection sensitivity. These modifications enable more sensitive MT detection than previously described blotting methods. In addition, this technique eliminates the need for indirect monitoring approaches and simplifies quantification since sample fractionation or enrichment are not required.

Risk for neuropathologically confirmed Alzheimer's disease and residual aluminum in municipal drinking water employing weighted residential histories

We investigated a possible relation between aluminum concentration ([Al]) in public drinking water and Alzheimer's disease (AD), with AD cases and controls defined on the basis of strict neuropathologic criteria. Using the case/control odds ratio as an estimate of relative risk and [Al] > or = 100 microgram/L as the cutoff point, elevated risks for histopathologically verified AD were associated with higher [Al]. Comparing all AD cases with all non-AD controls, and using the [Al] of public drinking water at last residence before death as the measure of exposure, the estimated relative risk associated with [Al] > or = 100 microgram/L was 1.7 (95% CI: 1.2-2.5). Estimating aluminum exposure from a 10-year weighted residential history resulted in estimates of relative risk of 2.5 or greater. The public health implications of the observed relationship between [Al] in drinking water and AD prevalence in the population depend in large measure on population exposure characteristics. In Ontario, it is estimated that 19% of the population was exposed to residual [Al] greater than or equal to 100 microgram/L. Based on the estimated relative risk and the assumption of causality, this translates to an etiologic fraction of 0.23. Although the potential contributions of confounding and mitigating factors are not defined in this report, the merit of limiting residual aluminum in drinking water supplies deserves serious attention.

A prospective study of the clinical utility of ApoE genotype in the prediction of outcome in patients with memory impairment

Given the relationship between the presence of ApoE epsilon 4 and Alzheimer's disease (AD), were studied whether knowledge of epsilon 4 status would predict which memory-impaired patients would develop AD over time. One hundred seven patients who presented with memory impairment but not dementia were referred to the study by their family physicians. These patients were followed prospectively over a 2-year period. Twenty-nine patients developed AD, while 78 did not develop dementia. We found that ApoE genotype was a reliable prognostic indicator of who developed AD in this group only when memory test performance was included in the predictive model. These findings indicate that limitations of ApoE genotyping in isolation as a prognostic indicator of AD. Because this study included prospectively selected patients who were followed longitudinally, our findings are likely to have more relevance in the clinical setting than those obtained from currently available retrospective studies.

Localization of a new ferritin heavy chain sequence present in human brain mRNA to chromosome 11

Two types of ferritin heavy (H) chain clones have been isolated from cDNA libraries of human fetal and adult brain: one corresponds to the ferritin H chain mRNA that is abundant in liver and is called "liver-like" brain cDNA; the other contains an additional 279 nucleotide (nt) sequence in the 3' untranslated region and is called brain ferritin H chain cDNA. To map the 279-nt sequence, polymerase chain reaction (PCR) amplification was carried out using DNA from rodent x human hybrid cell lines containing single human chromosomes as templates, and oligomeric primers homologous to the 3' end of the 279-nt sequence (primer A) and to a coding sequence just 5' to the 279-nt sequence. Significant PCR product of the size expected from analysis of the brain ferritin H chain cDNA clones and a genomic ferritin H chain clone (487 bp) was generated only from hybrid-cell DNA containing human chromosome 11. This PCR product and the "liver-like" brain cDNA (lacking the 279-nt sequence) both hybridized to chromosome 11 fragments that are known to define the well-characterized functional liver ferritin H chain gene and a putative pseudogene. Preliminary data indicate that primer A (and thus the 279-nt sequence) maps to the functional ferritin H chain gene fragments, but binding to the pseudogene has not been ruled out.

Conformation and fibrillogenesis of Alzheimer A beta peptides with selected substitution of charged residues

A key pathological feature of Alzheimer's disease (AD) is the formation and accumulation of amyloid fibers within the neurophil as senile plaques and in the walls of cerebral and meningeal blood vessels. The major component is the 39 to 42 residue amyloid beta protein (A beta), which is an internal proteolytic fragment of the membrane-associated amyloid precursor protein. Aggregation of A beta into amyloid fibers that could be cytotoxic may be a factor in the AD-related neuronal loss. To understand the steps and molecular interactions involved in the transition from a soluble to fibrous form of A beta, and to test molecular models that postulate ion pairing between beta-strands, we have synthetized four peptides having substitutions in specific, charged residues. These included an A beta fragment, residues 11 to 25, and having histidine-to-aspartate replacements at positions 13 (H13D) and 14 (H14D), an aspartate-to-lysine at position 23 (D23K) and a 28-mer full-length extracellular domain where the positive charge cluster at His13-His14-Gln15-Lys16 was replaced by an uncharged Gly13-Gly14-Gln15-Gly16 (GGQG). Fourier-transform infrared spectroscopy and fiber X-ray diffraction determined that the H13D and H14D substitutions had negligible effect on beta-sheet formation, suggesting that these residues are not critical for the intramolecular interactions necessary for folding in the beta-conformation. However, negative-stain electron microscopy revealed that the loss of the His13 or His14 resulted in only protofilament formation, suggesting that these residues are involved in amyloid fibril assembly. By contrast, the D23K substitution virtually eliminated folding into a beta-sheet conformation, with appreciable secondary structure being detected only following extended incubation times. The complete absence of the centrally charged region GGQG arrested amyloid assembly at the protofilament stage and also reduced the stability of the beta-conformation, suggesting a contribution of Lys16 in maintaining secondary structure. While it has been conclusively demonstrated by previous investigations that amyloid formation is dependent to a large extent on hydrophobically driven interactions, our results indicate that charge-charge interactions function in concert with non-ionic interactions to stabilize the beta-sheet conformation and assembly of AD amyloid fibers.

Analysis of the functional effects of a mutation in SOD1 associated with familial amyotrophic lateral sclerosis

Mutations in the Cu, Zn superoxide dismutase (SOD1) gene have been reported in some pedigrees with Familial Amyotrophic Lateral Sclerosis (FALS). We have investigated the functional and structural effects of a Gly-->Ser mutation at codon 41 of SOD1 in a pedigree with FALS and the topography of SOD1 expression in the mammalian CNS. These analyses show that the 41Gly-->Ser mutation causes a 27% reduction in Cu, Zn SOD activity. SOD1 is transcribed at high levels in rat motoneurons and four other types of neurons homologous to upper motoneurons that degenerate in human ALS. However, SOD1 is transcribed at lower levels in other types of neurons, such as cerebellar Purkinje cells, which are not usually involved significantly in human ALS. On the other hand, immunocytochemical studies indicate that most types of rat neurons contain similar levels of Cu, Zn SOD immunoreactive protein. Nevertheless, these results suggest that the essential feature causing this subtype of ALS is either a reduction in Cu, Zn SOD activity in cell types that presumably critically require Cu, Zn SOD for protection against oxidative damage or the fact that the mutation in SOD1 associated with FALS results in a novel gain of function that is particularly deleterious to those cell types expressing SOD1 at high levels.

Are the associations between Alzheimer's disease and polymorphisms in the apolipoprotein E and the apolipoprotein CII genes due to linkage disequilibrium?

Allele frequencies for polymorphisms in the apolipoprotein E and the apolipoprotein CII genes were determined in subjects of Ashkenazi Jewish origin with late-onset Alzheimer's disease and in unaffected control subjects from the same ethnic group. A significant association was observed between late-onset Alzheimer's disease and the epsilon 4 (112Cys-->Arg) allele of apolipoprotein E; however, no association was detected with apolipoprotein CII. These results suggest that the association with epsilon 4 is probably not due to linkage disequilibrium.

Machado-Joseph disease in pedigrees of Azorean descent is linked to chromosome 14

A locus for Machado-Joseph disease (MJD) has recently been mapped to a 30-cM region of chromosome 14q in five pedigrees of Japanese descent. MJD is a clinically pleomorphic neurodegenerative disease that was originally described in subjects of Azorean descent. In light of the nonallelic heterogeneity in other inherited spinocerebellar ataxias, we were interested to determine if the MJD phenotype in Japanese and Azorean pedigrees arose from mutations at the same locus. We provide evidence that MJD in five pedigrees of Azorean descent is also linked to chromosome 14q in an 18-cM region between the markers D14S67 and AACT (multipoint lod score +7.00 near D14S81). We also report molecular evidence for homozygosity at the MJD locus in an MJD-affected subject with severe, early-onset symptoms. These observations confirm the initial report of linkage of MJD to chromosome 14; suggest that MJD in Japanese and Azorean subjects may represent allelic or identical mutations at the same locus; and provide one possible explanation (MJD gene dosage) for the observed phenotypic heterogeneity in this disease.

Generation and characterization of novel antibodies highly selective for phosphorylated linker histone H1 in Tetrahymena and HeLa cells

Phosphorylated forms of Tetrahymena macronuclear histone H1 were separated from each other and from dephosphorylated H1 by cation-exchange HPLC. A homogeneous fraction of hyperphosphorylated macronuclear H1 was then used to generate novel polyclonal antibodies highly selective for phosphorylated H1 in Tetrahymena and in human cells. These antibodies fail to recognize dephosphorylated forms of H1 in both organisms and are not reactive with most other nuclear or cytoplasmic phosphoproteins including those induced during mitosis. The selectivity of these antibodies for phosphorylated forms of H1 in Tetrahymena and in HeLa argues strongly that these antibodies recognize highly conserved phosphorylated epitopes found in most H1s and from this standpoint Tetrahymena H1 is not atypical. Using these antibodies in indirect immunofluorescence analyses, we find that a significant fraction of interphase mammalian cells display a strikingly punctate pattern of nuclear fluorescence. As cells enter S-phase, nuclear staining becomes more diffuse, increases significantly, and continues to increase as cells enter mitosis. As cells exit from mitosis, staining with the anti-phosphorylated H1 antibodies is rapidly lost presumably owing to the dephosphorylation of H1. These immunofluorescent data document precisely the cell cycle changes in the level of H1 phosphorylation determined by earlier biochemical studies and suggest that these antibodies represent a powerful new tool to probe the function(s) of H1 phosphorylation in a wide variety of eukaryotic systems.

Protein-DNA interactions in the promoter region of the amyloid precursor protein (APP) gene in human neocortex

We have investigated protein-DNA interactions in the proximal promoter of the human amyloid precursor protein (APP) gene in temporal lobe neocortical nuclei isolated from control and Alzheimer disease (AD) affected brains. We report that the human APP 5' promoter sequence from -203 to +55 bp, which has been previously reported to contain essential regulatory elements for APP gene transcription, lies in a deoxyribonuclease I, micrococcal nuclease- and restriction endonuclease-sensitive, G+C-rich nucleosome-free gap flanked both 5' and 3' by typical nucleosome structures. As analyzed by electrophoretic mobility shift assay, this extended internucleosomal linker DNA is heavily occupied by nuclear protein factors, and interacts differentially with nuclear protein extracts obtained from HeLa and human brain neocortical nuclei. This suggests that the chromatin conformation of the APP gene promoter may vary in different cell types, and may correlate with differences in APP gene expression. Human recombinant transcription factors AP1, SP1 and TFIID (but not AP2 or brain histones H1, H2B and H4) interact with the -203 to +55 bp of the human APP promoter sequence. Only minor differences were observed in the chromatin structure of the immediate APP promoter between non-AD and AD affected neocortical nuclei, suggesting either that post-transcriptional processes, or that regulatory elements lying elsewhere in the APP gene may be important in the aberrant accumulation of the APP gene product.

Alzheimer A beta amyloid forms an inhibitory neuronal substrate

Alzheimer's disease (AD) is identified by the accumulation of amyloid plaques, neurofibrillary degeneration, and the accompanying neuronal loss. AD amyloid assembles into compact fibrous deposits from the amyloid beta (A beta) protein, which is a proteolytic fragment of the membrane-associated amyloid precursor protein. To examine the effects of amyloid on neuron growth, a hybrid mouse motoneuron cell line (NSC34) exhibiting spontaneous process formation was exposed to artificial "plaques" created from aggregated synthetic A beta peptides. These correspond to full-length A beta residues 1-40 (A beta 1-40), an internal beta-sheet region comprising residues 11-28 (A beta 11-28), and a proposed toxic fragment comprising residues 25-35 (A beta 25-35). Fibers were immobilized onto culture dishes, and addition of cells to these in vitro plaques revealed that A beta was not a permissive substrate for cell adhesion. Neurites in close contact with these deposits displayed abnormal swelling and a tendency to avoid contact with the A beta fibers. In contrast, A beta did not affect the adhesion or growth of rat astrocytes, implicating a specific A beta-neuron relationship. The inhibitory effects were also unique to A beta as no response was observed to deposits of pancreatic islet amyloid polypeptide fibers. Considering the importance of cell adhesion in neurite elongation and axonal guidance, the antiadhesive properties of A beta amyloid plaques found in vivo may contribute to the neuronal loss responsible for the clinical manifestations of AD.

SOD1 missense mutation in an Italian family with ALS

We have discovered a new Italian pedigree with autosomal-dominant ALS. The pedigree, at present, comprises 75 members distributed in five generations. ALS was diagnosed in eight patients. The mean +/- SD age of onset of the disease was 46.8 +/- 13.5 years, with a range of 29 to 63 years. The mean +/- SD duration of the disease was 11.6 +/- 1.7 months. Molecular genetic studies showed a missense mutation (Gly-->Ser, codon 41) in exon 2 of the Cu/Zn superoxide dismutase gene (SOD1) on chromosome 21 in the available affected member and in 45% of the at-risk subjects of the pedigree. This study confirms the presence of SOD1 point mutations in families with autosomal-dominant ALS and suggests that additional genetic or environmental factors may be involved in the full expression of the disease.

Desferrioxamine and Alzheimer's disease: video home behavior assessment of clinical course and measures of brain aluminum

Drug trials designed to modify the progression of Alzheimer's disease (AD) have required the development of mental state and behavior evaluation instruments that are sensitive to cognitive decline and measure skills useful in everyday living. We describe a videotaped home behavior (VHB) assessment instrument with high construct validity and reliability and a strong relationship to criterion references. The VHB was employed to test the hypothesis that aluminum is an important pathogenic factor in AD. The trivalent chelating agent desferrioxamine (DFO), 125 mg i.m. twice daily five days per week, was used in a randomized single-blind, oral lecithin, placebo-controlled clinical trial in 48 patients with AD. Analysis showed that the treatment and no-treatment groups were closely matched at entry into the trial but that the rate of decline, as measured by the VHB over 2 years of observation, was twice as rapid in the no-treatment group compared with the DFO-treated group. Furthermore, trace-metal analysis of autopsied brain confirmed that extended treatment with DFO lowered neocortical brain aluminum concentrations to near control concentrations. Aluminum ion-specific chelation may be a useful palliative treatment for AD, and further clinical trials are indicated.

Biochemistry of Alzheimer's disease amyloid plaques

One of the principal identifying features of Alzheimer's disease (AD) is the extracellular deposition of fibrous protein aggregates in the form of amyloid plaques. The major component of these deposits is the amyloid beta (A beta) protein that is a proteolytic fragment of the integral membrane amyloid precursor protein (APP). Understanding the pathways responsible for A beta formation and the mechanism by which it accumulates within the brain could provide key answers to AD pathogenesis. This review will explore the biochemistry of A beta and its precursor, the possible causal relationship between amyloid and AD-associated neuronal death, the role of additional cellular elements in amyloid formation, and the potential application of these components in clinical diagnosis.

Family with 22-derived marker chromosome and late-onset dementia of the Alzheimer type: II. Further cytogenetic analysis of the marker and characterization of the high-level repeat sequences using fluorescence in situ hybridization

We have further characterized an unusual 22p+ marker chromosome with a double nucleolus organizer region (dNOR) previously identified in a family with late-onset dementia of the Alzheimer type. G-banding and morphology of the marker's q arm were typically normal. However, the p+ arm had a terminal cytological satellite and a GT-positive region at the midpoint. Standard C-banding documented 2 C-positive regions: one was associated with the primary centromere; the other, which was at the midpoint of the p arm, was not associated with a constriction. With replication-banding, there was a darkly staining region in the middle of the p+ arm that resembled the pericentromeric region of a chromosome 21 or 22. Fluorescence in situ hybridization with pXlr 101, a probe recognizing the full repeating unit of rDNA, indicated that the marker had an unusually larger rDNA region; with pU 1.2, a probe recognizing the human rDNA promoter, the signal was a doublet. The marker had 2 signals with a beta-satellite probe, and a second signal in addition to that present at the primary centromere under low stringency with alpha-satellite probes and a classic satellite probe. Immunostaining of chromosome spreads after R-banding and ultraviolet (UV) denaturation showed that the major portion of the marker's p arm was highly methylated.

Alpha 1-antichymotrypsin binding to Alzheimer A beta peptides is sequence specific and induces fibril disaggregation in vitro

The serine protease inhibitor alpha 1-antichymotrypsin (ACT) consistently colocalizes with amyloid deposits of Alzheimer's disease (AD) and may contribute to the generation of amyloid proteins and/or physically affect fibril assembly. AD amyloid fibrils are composed primarily of A beta, which is a proteolytic fragment of the larger beta-amyloid precursor protein. Using negative-stain and immunochemical electron microscopy, we have investigated the binding of ACT to the fibrils formed by four synthetic A beta analogues corresponding to the wild-type human 1-40 sequence [Hwt(1-40)], a 1-40 peptide [HDu(1-40)] containing the Glu22-->Gln mutation found in hereditary cerebral hemorrhage with amyloidosis of the Dutch type, the N-terminal 1-28 residues [beta(1-28)], and an internal fragment of A beta containing residues 11-28 [beta(11-28)]. Each of these peptide analogues assembled into 70-90-A-diameter fibrils resembling native amyloid and, except for beta(11-28), bound ACT, as indicated by the appearance of 80-100-A globular particles that adhered to preformed fibrils and that could be decorated with anti-ACT antibodies. Under the conditions used, ACT binding destabilized the in vitro fibrils and produced a gradual dissolution of the macromolecular assemblies into constituent filaments and shorter fragments. The internal fragment (11-28) did not exhibit ACT binding or any structural changes. These results suggest that a specific sequence likely contained within the N-terminal 10 residues of A beta is responsible for the formation of the ACT-amyloid complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of calbindin-28k mRNA levels in Alzheimer as compared to Huntington hippocampus

Disturbances in calcium homeostasis have been observed to be associated with Alzheimer's and other neurodegenerative diseases. Increased total calcium levels and decreased levels of calcium binding proteins have been found in Alzheimer brain tissue. However, the mechanism behind these disturbances remain unknown. In situ hybridization with tritiated antisense RNA probes for the calcium binding proteins, calbindin-28k and calmodulin, was used to examine the expression of genes coding for these proteins in Alzheimer and Huntington brain tissues matched for age, agonal process and autopsy interval. mRNA levels for calbindin-28k were reduced by 35% in CA1 and CA2 regions of Alzheimer hippocampus, as compared to Huntington control. In contrast, calmodulin expression was unchanged in CA1 but reduced by 30% in CA2. mRNA expression of calbindin-28k and calmodulin in Alzheimer temporal cortex did not differ from control. There were no significant differences in calcium binding protein message levels in cerebellar Purkinje cells between Alzheimer and Huntington control. There was no correlation between calcium binding protein message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, decreased calbindin-28k expression in Alzheimer-affected hippocampus was due to an increase in the percentage of neurons expressing lower message levels for these proteins.

Age-associated chromosome 21 loss in Down syndrome: possible relevance to mosaicism and Alzheimer disease

We previously observed low level mosaicism (2-4% normal cells) in phytohemagglutinin-stimulated peripheral blood lymphocytes (PBL) in 29% of a small group of elderly persons with Down syndrome (DS). An analysis of cytogenetic data on 154 trisomy 21 cases (age 1 day to 68 years) showed that the proportion of diploid cells in such cultures significantly increased (P < 0.005) with advancing age. Thus, the "occult" mosaicism in PBL of the elderly persons with DS is likely due to the accumulation of cells that have lost a chromosome 21. A consequence of chromosome 21 loss could be uniparental disomy of the 2n cells, a factor that might have significant biological consequences if some chromosome 21 genes are imprinted. Loss of a chromosome 21 from trisomic cells might result in tissue-specific mosaicism and "classical" mosaicism in different age groups. Chromosome 21 loss might also be relevant to the development of Alzheimer-type dementia in DS and in the general population.

A predictor for side effects in patients with Alzheimer's disease treated with deferoxamine mesylate

In a previously reported clinical trial, patients with Alzheimer's disease were treated with deferoxamine mesylate, which resulted in a 50% reduction in the average rate of deterioration over 2 years. There were five deaths in the untreated group during the trial and no deaths in the treated group, although five of 25 treated patients reported anorexia. Deferoxamine metabolite analysis of urine for 24 hours after deferoxamine injection from sensitive and nonsensitive patients showed marked differences. Occurrence of side effects correlated with increased formation of a monoamine oxidase catalyzed (major) metabolite, MFO1. The metabolite ratio, MFO1/total metabolites, plus parent drug (TOT) showed a bimodal distribution with a mean +/- SD value of 0.68 +/- 0.06 for the nonsensitive and 0.79 +/- 0.04 for sensitive patients. The MFO1/TOT ratio discriminates between sensitive and nonsensitive patients, and we suggest that the half difference mark between the two mean values (0.735) can be used as a predictor of side effects. Patients with a MFO1/TOT ratio of greater than 0.70 would be considered at risk and observed for onset of side effects. Patients with a MFO1/TOT ratio greater than 0.80 would be considered for immediate adjunct treatment with isoniazid or other monoamine oxidase inhibitors.

Resolution of serum aluminum-binding proteins by size-exclusion chromatography: identification of a new carrier of aluminum in human serum

We have examined the use of TSK-GEL HW 55S for determining the distribution of aluminum in human serum by size-exclusion chromatography (SEC). In comparison to other SEC matrices, this material has less affinity for ionized aluminum and separates serum proteins and their aluminum complexes with greater resolution. This enabled the identification of a previously unknown protein carrier, provisionally called albindin, that binds aluminum with great stability. Albindin appears to be distinct from the previously described aluminum carriers albumin and transferrin and may be important in the pathogenesis of disease secondary to hyperaluminemia.

Aluminum-binding serum proteins: desferrioxamine alters serum aluminum speciation

The aluminum content of four size classes of protein (high and low molecular weight, transferrin/albumin and a fraction provisionally termed albindin) in sera from healthy volunteers (group I) and from aluminum workers with normal (group II) and high (group III) total serum aluminum was compared using size exclusion chromatography and electrothermal atomic absorption spectroscopy. In the absence of any drug treatment the transferrin/albumin fraction was the major carrier, containing 29% to 33% of the aluminum recovered, in all three subject groups. Desferrioxamine treatment of groups II and III significantly decreased the proportion of aluminum bound by albumin/transferrin (P less than 0.05 in group III) and increased that bound by albindin (P less than 0.05 in groups II and III). The albindin fraction contained over 40% of the aluminum recovered from sera of group III subjects during desferrioxamine treatment. We conclude that the albindin fraction contains a protein or proteins that can form stable complexes with aluminum which may be important in preventing aluminum toxicity.

Reduction of vitamin D hormone receptor mRNA levels in Alzheimer as compared to Huntington hippocampus: correlation with calbindin-28k mRNA levels

Receptors for vitamin D hormone (VDR) and the calcium binding protein, calbindin-28k, have been localized in many tissues, including brain. In brain, VDR and calbindin-28k were reported to colocalize in hippocampal CA1 cells. We have shown that mRNA pool size for calbindin-28k was reduced, on average, by 35% in Alzheimer hippocampal CA1 cells, as compared to Huntington control (manuscript in preparation). In the present study, in situ hybridization with tritiated antisense RNA probes was used to examine VDR expression in paired Alzheimer and Huntington brain tissue. Message levels for VDR were reduced, on average, by 34% and 31%, respectively, in Alzheimer hippocampal CA1 and CA2 pyramidal cells, as compared to Huntington control. However, VDR message levels were not significantly different from control in Alzheimer temporal cortex or cerebellum. There was no correlation between VDR message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, VDR mRNA pool size in hippocampal CA1 cells correlated significantly with calbindin-28k message levels (r = 0.52, P less than 0.001). Decreased message levels for VDR and calbindin-28k in these cells were due to an increased percentage of cells expressing lower message levels for these proteins. These results show that in Alzheimer hippocampal CA1 cells, VDR mRNA pool size is downregulated and that this downregulation may play a role in the reduction of calbindin-28k expression.

Reduction of thyroid hormone receptor c-ERB A alpha mRNA levels in the hippocampus of Alzheimer as compared to Huntington brain

A history of thyroid dysfunction has been cited as a possible risk factor for Alzheimer's disease (AD). Neurologic symptoms displayed by hypothyroid patients resemble, in part, those manifested by Alzheimer patients. To determine if a relationship exists between thyroid hormone receptor message levels and AD, in situ hybridization with tritiated antisense RNA probes for thyroid hormone receptors was used to examine the expression of these genes in Alzheimer and Huntington brain tissue. Message levels for a thyroid hormone receptor highly expressed in brain (c-ERB A alpha) was reduced by 52% in CA1 and 43% in CA2 in Alzheimer hippocampus as compared to Huntington controls. In contrast, message levels for another form of thyroid hormone receptor (c-ERB A beta 1) in Alzheimer hippocampus were not significantly different from Huntington controls. Temporal and cerebellar levels of c-ERB A alpha were elevated by 1.6-fold whereas temporal but not cerebellar levels of c-ERB A beta 1 were elevated 2.0-fold in Alzheimer brain. There was no correlation between thyroid hormone receptor levels and brain weight, autopsy interval, patient age, or the extent of neurofibrillary degeneration. Instead, decreased thyroid hormone receptor mRNA levels in Alzheimer-affected hippocampus were due to an increase in the percentage of neurons expressing lower message levels for these proteins.

Would decreased aluminum ingestion reduce the incidence of Alzheimer's disease?

Although the cause of Alzheimer's disease (AD) remains unknown there is mounting evidence that implicates aluminum as a toxic environmental factor of considerable importance. Four independent lines of evidence--laboratory studies of the effects of intracerebral aluminum on the cognitive and memory performance of animals, biochemical studies, epidemiologic studies and the slowing of the progress of the disease with the use of an agent that removes aluminum from the body--now support the concept that aluminum is one of the pathogenic factors in AD. The evidence warrants serious consideration of reducing human exposure to aluminum. We hypothesize that a public health effort to restrict human ingestion of aluminum would reduce the incidence of this common chronic illness in the elderly.

Anomalous gene expression in Alzheimer disease: cause or effect

Altered chromatin conformation and increased amounts of aluminum have been observed in the brains of patients with Alzheimer disease. These factors have been shown to affect gene regulation. In this report, we describe how these changes may selectively alter the pool size of the human light chain neurofilament gene and play a fundamental role in the expression of this disease.

Localization and quantitation of 68 kDa neurofilament and superoxide dismutase-1 mRNA in Alzheimer brains

The technique of in situ hybridization with tritiated RNA probes was used to study the expression of the 68 kDa neurofilament (NF68) gene and the superoxide dismutase-1 (SOD-1) gene in the brains of Alzheimer's disease (AD) patients. Messenger RNA (mRNA) for these proteins was localized and quantified in single cells of formalin-fixed, paraffin-embedded sections of 4 pairs of AD and Huntington's disease (HD) brains from patients matched for age at death and autopsy interval. The cerebellar cortex and hippocampal CA1 and CA2 regions were compared in these two groups of subjects, since in AD the CA2 region of the hippocampus and the cerebellum have been found to be relatively unaffected by the Alzheimer process in comparison to the hippocampal CA1 region. The amount of NF68 mRNA was reduced by approximately 50% in pyramidal cells of both the CA1 and CA2 of AD hippocampus (P less than 0.001), and by 15% in the Purkinje cells of AD cerebellum (P less than 0.05) relative to that of the HD individuals. SOD-1 mRNA was reduced by about 22% in the CA1 of AD brains (P less than 0.001) with no corresponding reduction in the CA2, and by only 5% in the AD cerebellum (P greater than 0.5). The paired design of the study suggests that these results are not simply attributable to the effects of autopsy interval or the agonal process in each patient's death.

A correlation between gene transcriptional activity and cerebral glucose metabolism in Alzheimer's disease-affected neocortex: cause or effect?

Our laboratory has measured mRNA pool sizes in neocortex afflicted with Alzheimer's disease (AD). We have observed a repression of gene expression in the temporal and parietal regions compared to age-matched control neocortex. These changes in messenger RNA pool size closely parallel the observed alterations in local cerebral metabolic rates for glucose (LCMR-g), as detected by positron emission tomography (PET). For example, deficits in both gene transcription and glucose metabolism appear to be the greatest in AD-affected superior temporal neocortex (Brodmann area 22) but are less apparent in the primary visual cortex (Brodmann area 17) or in the cerebellum. The unresolved question is whether changes in gene expression are the cause or effect of altered glucose metabolism. However, the non-random reductions in the pool size for certain neocortical mRNAs argue in favour of altered gene expression as the primary event.

Cytoskeletal messenger RNA stability in human neocortex: studies in normal aging and in Alzheimer's disease

Total RNA was extracted from human brain temporal and parietotemporal neocortical grey matter with postmortem intervals (PMI) of up to 13.5 hours. The integrity and rank abundance of heterogeneous nuclear RNA (HnRNA) and messenger RNA (mRNA) were analyzed by Northern gel dot blot hybridization with specific cloned probes of neurobiological interest: the RNA messages for four cytoskeletal components including glial fibrillary acidic protein (GFAP), alpha-tubulin, beta-actin and the human neurofilament light chain (HNF-L) genomic sequence, the Alu repetitive element, the scrapie prion PrP DNA probe and the chromatin condensing agent linker histone H1(0) genomic probe. Our observations indicate that for the cytoskeletal RNA messages studied here: (1) short postmortem intervals (of up to 4.5 hours) had only small effects upon RNA quality in these neocortices, (2) GFAP and HNF-L transcripts were represented at relatively high levels in the cerebral neocortex and (3) each RNA species in normal human brain had both unique and characteristic intracellular levels of abundance and decay kinetics. In the pathological condition, Alzheimer's disease (AD), cells of the temporal and parietotemporal neocortices of afflicted brains showed selective reductions in cytoskeletal RNA pool size which are not attributable to RNA transcript stability.

Effect of exposure of miners to aluminium powder

'McIntyre Powder' (finely ground aluminium and aluminium oxide) was used as a prophylactic agent against silicotic lung disease between 1944 and 1979 in mines in northern Ontario. To find out whether the practice produced neurotoxic effects a morbidity prevalence study was conducted between 1988 and 1989. There were no significant differences between exposed and non-exposed miners in reported diagnoses of neurological disorder; however, exposed miners performed less well than did unexposed workers on cognitive state examinations; also, the proportion of men with scores in the impaired range was greater in the exposed than non-exposed group. Likelihood of scores in the impaired range increased with duration of exposure. The findings are consistent with putative neurotoxicity of chronic aluminium exposure.

Suppression of deferoxamine mesylate treatment-induced side effects by coadministration of isoniazid in a patient with Alzheimer's disease subject to aluminum removal by ionspecific chelation

Deferoxamine treatment may produce serious side effects that can be eliminated by modification of treatment and by control of deferoxamine metabolism. A patient suffering from dementia of the Alzheimer type with normal liver and kidney function who was treated with deferoxamine initially tolerated a dose of 7 mg/kg deferoxamine mesylate injected intramuscularly twice a day for a total of 5 days a week. After several months nausea and weight loss gradually developed in the patient that could be controlled initially by dose reduction, leading to levels inappropriate for aluminum chelation. HPLC analysis of blood and urine revealed several metabolites including, as a major component, a plasma monoamine oxidase (MAO) catalyzed end product MFO1. Coadministration of isoniazid, a plasma MAO inhibitor, with deferoxamine resulted in reduction of MFO1 from 81% to 8% accompanied by increases in the amounts of metabolite 2 (MFO2) from 2% to 24% and unmetabolized deferoxamine from 17% to 68% after 6 months of treatment. The side effects subsided, the patient regained weight, and treatment could be continued.

Brain amino acid contents are dissimilar in sporadic and Guamanian amyotrophic lateral sclerosis

Amino acid contents were measured in autopsied brains of five Guamanian patients with amyotrophic lateral sclerosis (ALS) or parkinsonism-dementia. Absence of the glutamate deficiency and taurine excess characteristic of sporadic ALS suggest that, despite clinical similarities, Guamanian ALS is a different disorder from sporadic ALS.

Red cell superoxide dismutase, glutathione peroxidase and catalase in Down syndrome patients with and without manifestations of Alzheimer disease

The activities of red blood cell enzymes that scavenge the superoxide radical and hydrogen peroxide were measured in severely to profoundly retarded adult Down syndrome (DS) patients with and without manifestations of Alzheimer disease (AD), and control individuals matched for sex, age, and time of blood sampling. Cu,Zn superoxide dismutase (SOD-1) and glutathione peroxidase (GSHPx) activities were significantly elevated (1.39-fold and 1.24-fold, respectively) in DS individuals without AD. When an adjustment was made for the SOD gene dosage effect, DS patients with AD manifestations had significantly lower SOD levels than the matched control individuals. In contrast, DS patients with and without AD had a similar elevation in GSHPx (an adaptive phenomenon). The mean catalase (CAT) activity was no different in DS and control individuals; however, in a paired regression analysis, DS patients without AD had marginally lower CAT activity than control individuals, whereas DS patients with AD had slightly but not significantly higher CAT activity. Thus, AD manifestations in this DS population are associated with changes in the red cell oxygen scavenging processes.

Development of an intravenous desferrioxamine mesylate treatment protocol for swine: monitoring of desferrioxamine and metabolites by high-performance liquid chromatography

Desferrioxamine (DFO) metabolism and its pharmacokinetics were studied in a swine model using high-performance liquid chromatography. DFO and three iron-binding metabolites occurred in plasma. Interindividual differences in pharmacokinetics and metabolism were observed. Urine analysis in 4 pigs showed three iron-binding metabolites. The mean percent dose excreted in urine in the form of the parent drug was 45 +/- 10% and 10 +/- 2% (means +/- SD) in the form of metabolites. Of the total amount of the parent drug infused, 3 h after initiation, 87% was in the form of DFO, whereas 13% was present as the DFO-iron III complex which represented 45 mg of urinary iron elimination. The described DFO infusion protocol provides for sufficient DFO to chelate significant amounts of ferric iron in excess of normal levels, thus allowing experimental studies of iron chelation in a variety of disease states.

New evidence for an active role of aluminum in Alzheimer's disease

Application of molecular biological techniques and sensitive elemental analysis have produced new evidence implicating aluminum as an important factor in down regulation of neuronal protein metabolism. Aluminum in Alzheimer's disease may act by electrostatically crosslinking proteins, particularly the methionine containing histone H1(0), and DNA. The consequence of such crosslinking is reduced transcription of at least one neuron specific gene, the low molecular weight component of neurofilaments. In the superior temporal gyrus in Alzheimer's disease, down regulation of this gene occurs in approximately 86% of surviving neurons and, therefore, aluminum must be considered as having an active role in the pathogenesis. Epidemiological studies are reviewed that independently support the hypothesis that environmental aluminum is a significant risk factor. Preliminary evidence also suggests that a disorder in phosphorylation may be an important initiating factor.

Linker histone-DNA complexes: enhanced stability in the presence of aluminum lactate and implications for Alzheimer's disease

The binding of human brain linker histone proteins to a radiolabelled human Alu repetitive element was examined by mobility shift assay. Analysis of the complexes formed from protein extracts of whole neocortical nuclei, under physiological conditions in vitro revealed that linker histone H1(0) has the highest affinity for the Alu DNA sequence. The linker histone-DNA complexes assembled in the presence of aluminum lactate were more resistant to sodium chloride-induced dissociation than those formed in the presence of sodium lactate. The enhanced stability of deoxyribonucleoprotein (DNP) complexes in the presence of the aluminum cation may be of significance in neurodegenerative conditions such as Alzheimer's disease where aluminum preferentially associates with DNA containing structures of the nucleus.

High-performance liquid chromatographic analysis of desferrioxamine. Pharmacokinetic and metabolic studies

A high-performance liquid chromatographic method has been developed that permits determination and quantitation of desferrioxamine and metabolites as their iron (III) complexes in small samples of mammalian plasma at levels encountered with ion-specific chelation treatments. The technique permits measurement of desferrioxamine and metabolite concentrations which can be used in pharmacokinetic studies. A human study is presented as an example.

Priming of semantic autobiographical knowledge: a case study of retrograde amnesia

The case of a 36-year-old man who suffers dense retrograde and anterograde amnesia as a result of closed-head injury that caused extensive damage to his left frontal-parietal and right parieto-occipital lobes is described. Patient K.C. has normal intelligence and relatively well-preserved perceptual, linguistic, short-term memory, and reasoning abilities. He possesses some fragmentary general knowledge about his autobiographical past, but he does not remember a single personal event or happening from any time of his life. He has some preserved expert knowledge related to the work he did for 3 years before the onset of amnesia, although he has no personal recollections from that period. Some features of K.C.'s retrograde amnesia can be interpreted in terms of the distinction between episodic and semantic memory, and in terms of the distinction between episodic and semantic autobiographical knowledge. K.C.'s semantic knowledge, but not his episodic knowledge, showed progressive improvement, or priming, in the course of the investigation.

Localization of the 68,000-Da human neurofilament gene (NF68) using a murine cDNA probe

A recent investigation, using a human genomic probe, has indicated that the 68,000 dalton neurofilament gene (NF68) is on the short arm of chromosome 8. We have used a murine cDNA probe on 65 metaphase spreads in situ to localize the human NF68 gene to 8p21 (20/370 grains; p less than 0.0001). In addition, we have found secondary hybridization sites at the centromeric region of chromosome 2 and the long arm of chromosome 7, which are putative loci for other intermediate filaments.

Selective messenger RNA reduction in Alzheimer's disease

The relative abundance of 7 messenger RNAs extracted from Alzheimer and control neocortex were examined by Northern and quantitative dot blot analysis. The average yield of mRNA coding for NF-L, the 68-kDa moiety of neurofilament protein, was reduced to 27% of control when expressed as the percentage of total RNA or 14% when expressed per gram of neocortex. In contrast, the yields of 6 other messenger RNAs fell into two categories: those which were statistically significantly reduced to about 65% of control and those which were not reduced when expressed as percentage of total RNA. The anomalous low abundance of neuron specific NF-L mRNA, coding for the lowest molecular weight moiety of neurofilament proteins, in cerebral cortex of Alzheimer's disease cannot be adequately accounted for by a non-specific effect of brain damage, neuron cell loss or neurons with neurofibrillary degeneration. We speculate that this mRNA decrease is related to a functional deficit of gene expression in Alzheimer's disease, perhaps related to the non-random increase in chromatin compaction previously reported from this laboratory. The inability of neurons to maintain homeostatic amounts of NF-L transcription products may be linked to the accumulation of abnormal filamentous components characteristically associated with the diseased cytoskeleton.

Origin and resolution of the aluminum controversy concerning Alzheimer's neurofibrillary degeneration

Elevated concentrations of aluminum are found in regions of neurofibrillary change in brains with senile or presenile dementia of Alzheimer's type. The concentrations of aluminum found in the human disease are comparable to those found in experimental animals with aluminum-induced neurofibrillary degeneration (NFD). Although there are a number of reports confirming these observations, two laboratories have been unable to detect elevated levels in Alzheimer's disease. We conducted an interlaboratory study to resolve this discrepancy and traced the discrepancy to difficulties in analytical procedures. We concluded that failure to detect elevated aluminum levels associated with NFD is the result of (a) lack of strict adherence to the criteria for sample selection; (b) selection of too large a sample for analysis; and (c) use of analytical methodology that has potential matrix interference for the measured signal.

Calmodulin and calbindin D28K in Alzheimer disease

The calcium binding proteins, calmodulin and calbindin D28K, were measured by radioimmunoassay in cerebral cortex from brains with degenerative brain diseases associated with dementia. Samples were obtained from 17 normal control brains, 18 Alzheimer affected brains, and 15 brains of patients who died of a dementia process other than Alzheimer disease. Calmodulin content in the non-Alzheimer group was not significantly different from control. However, in the Alzheimer group, frontal, temporal, parietal cortex, and subjacent white matter calmodulin content was significantly reduced (66% of that found in the other 2 groups). Calmodulin extracted from temporal cortex also demonstrated reduced efficacy as an activator of 3',5' cyclic nucleotide phosphodiesterase. Calbindin D28K was reduced both in Alzheimer and non-Alzheimer dementia brains. Reduced concentrations of these important proteins may affect calcium homeostasis and the regulation of a large number of calcium mediated brain functions.