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Peter Davies

Publications and source records attributed to Peter Davies.

At least 37 records · Page 2Linked to original sources
PubMed2005

Correlation of cerebrospinal fluid levels of tau protein phosphorylated at threonine 231 with rates of hippocampal atrophy in Alzheimer disease.

BACKGROUND: The microtubule-associated tau protein abnormally phosphorylated at threonine 231 (p-tau231) has been investigated as a potential marker of Alzheimer disease. Levels of cerebrospinal fluid (CSF) p-tau231 vary across patients with Alzheimer disease. We hypothesized that these variations partially reflect differences in the degree of neuronal damage and therefore may be used to predict structural disease progression. OBJECTIVE: To investigate whether CSF p-tau231 levels correlate with rates of hippocampal atrophy as an in vivo marker of regional neuronal loss. DESIGN AND PATIENTS: We measured hippocampal volumes on the basis of serial magnetic resonance image examinations in 22 patients with Alzheimer disease. In addition, we determined CSF p-tau231 levels at baseline. RESULTS: Levels of CSF p-tau231 were significantly correlated with baseline hippocampal volumes (P<.001) and rates of hippocampal atrophy (left hippocampus, P<.001; right hippocampus, P = .02), independent of disease duration and severity. CONCLUSION: These findings suggest that variations in p-tau231 levels may be used to predict progression of brain atrophy in patients with Alzheimer disease.

Aged↗
PubMed2005

Glutathione S-transferase hGSTM3 and ageing-associated neurodegeneration: relationship to Alzheimer's disease.

Glutathione S-transferases (GSTs) are detoxification enzymes that can counter ageing-associated oxidative and chemical stresses. The transcript of a distinct subclass of human GSTs (hGSTM3) was shown by RNA blot analysis to be widely distributed in different regions of adult brain. HPLC profiles indicated that the hGSTM3 subunit was the second most abundant GST subunit in brain. Immunocytochemistry performed with hGSTM3-specific antisera, showed prominent staining of neuritic plaques, neurofibrillary tangles and microglia in sections of hippocampus obtained from patients with Alzheimer's disease. The staining pattern was distinct from that obtained with normal brains. Because hGSTM3 is rich in cysteine residues and readily undergoes S-glutathiolation reactions, deposition of this protein could originate from cross-links produced by oxidative stress.

Aging↗
PubMed2005

Increased frequency of argyrophilic grain disease in Alzheimer disease with 4R tau-specific immunohistochemistry.

Argyrophilic grain disease (AGD) is a medial temporal 4R tauopathy with filamentous inclusions in dendrospinal portions of neurons. AGD is often associated with mild Alzheimer-type pathology, but it is difficult to detect AGD in the setting of advanced Alzheimer disease (AD). The frequency of AGD in AD has been difficult to determine because of masking of grains by neurofibrillary lesions. To address this issue, medial temporal lobe sections from AD brains were immunostained with a 4R tau-specific antibody, ET3, which permitted detection of grains even in the setting of advanced neurofibrillary degeneration. AGD was found in 61 of 239 AD cases (26%). The frequency of AGD in AD in this study is higher than in previous studies that relied on less selective staining methods, such as the Gallyas silver stain or immunostaining with phospho-tau antibodies. The frequency of AGD in AD did not correlate with Braak stage or with the density of neurofibrillary tangles and senile plaques in the limbic lobe; however, AD cases with AGD were significantly older than cases without AGD. The MAPT H1 frequency tended to be higher in AD cases with AGD than in those without AGD, but there were no differences in APOE epsilon4 carrier state. These findings suggest advanced age and possibly MAPT H1 are risk factors for AGD, even in the setting of concurrent AD, in which neurofibrillary degeneration is associated with accumulation of both 3R and 4R tau.

Aged↗
PubMed2005

Decreased neprilysin immunoreactivity in Alzheimer disease, but not in pathological aging.

Although evidence suggests that extensive cortical beta-amyloid (Abeta) deposition is essential in Alzheimer disease (AD), it is also detected in nondemented elderly individuals with pathologic aging (PA). Given evidence that neutral endopeptidase (NEP) or neprilysin, a key enzyme for clearance of Abeta, is decreased in AD, the goal of the present study was to determine if NEP was also decreased in PA. We measured NEP immunoreactivity in frontal cortex of 12 AD and six PA cases and compared this with 10 normal (N) elderly individuals. None had any significant other pathology, and they were similar with respect to age, sex, and postmortem delay. In addition, Abeta1-40 and Abeta1-42 were measured by enzyme-linked immunosorbent assay (ELISA), whereas tau, synaptophysin, and alpha-synuclein were measured on Western blots. The AD cases had more neuritic plaques, neurofibrillary tangles, higher Braak stage, and more tau immunoreactivity in frontal cortex than both PA and N. In contrast, both PA and AD had more senile plaques and Abeta1-42 than N. NEP immunoreactivity was decreased in AD but not in PA. The decrease was unlikely the result of neuronal or synaptic loss because NEP immunoreactivity in frontotemporal degeneration with comparable degrees of synaptic loss as the AD cases was not different from control subjects. Although NEP enzyme activity was decreased in approximately half the AD cases, on average, it was not decreased compared with N or PA. The results add further evidence that PA is distinct from AD and indicate that decreased Abeta degradation by NEP is unlikely to contribute significantly to amyloid deposition in PA or, in many cases, of AD.

Aged↗
PubMed2005

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Delivery of Health Care↗
PubMed2004

Tau paired helical filaments from Alzheimer's disease brain and assembled in vitro are based on beta-structure in the core domain.

Tau protein, a neuronal microtubule-associated protein, forms insoluble fibers ("paired helical filaments") in Alzheimer's disease and other tauopathies. Conflicting views on the structure of the fibers have been proposed recently, ranging from mainly alpha-helical structure to mainly beta-sheet, or a mixture of mostly random coil and beta-sheet. We have addressed this issue by studying tau fibers immunopurified from Alzheimer brain tissue by a conformation-specific antibody and comparing them with fibers reassembled from recombinant tau or tau constructs in vitro, using a combination of electron microscopy and spectroscopic methods. Brain-derived fibers and reassembled fibers both exhibit a typical twisted appearance when examined by electron microscopy. The soluble tau protein is a natively unfolded protein dominated by random coil structure, whereas Alzheimer PHFs and reassembled fibers show a shift toward an increase in the level of beta-structure. The results support a model in which the repeat domain of tau (which lies within the core of PHFs) adopts an increasing level of beta-structure during aggregation, whereas the N- and C-terminal domains projecting away from the PHF core are mostly random coil.

Alzheimer Disease↗
PubMed2004

Measurement of phosphorylated tau epitopes in the differential diagnosis of Alzheimer disease: a comparative cerebrospinal fluid study.

BACKGROUND: Abnormal hyperphosphorylation of the microtubule-associated protein tau and its incorporation into neurofibrillary tangles are major hallmarks of the pathogenesis of Alzheimer disease (AD). Different tau phosphoepitopes can be sensitively detected in cerebrospinal fluid (CSF). OBJECTIVE: To compare the diagnostic accuracy of CSF concentrations of tau proteins phosphorylated at 3 pathophysiologically important epitopes (p-tau) to discriminate among patients with AD, nondemented control subjects, and patients with other dementias. DESIGN AND SETTING: Cross-sectional, bicenter, memory clinic-based studies. PARTICIPANTS: One hundred sixty-one patients with a clinical diagnosis of AD, frontotemporal dementia, dementia with Lewy bodies, or vascular dementia and 45 nondemented controls (N = 206). MAIN OUTCOME MEASURES: Levels of tau protein phosphorylated at threonine 231 (p-tau231), threonine 181 (p-tau181), and serine 199 (p-tau199). The CSF p-tau protein levels were measured using 3 different enzyme-linked immunosorbent assays. RESULTS: The mean CSF levels of the studied p-tau proteins were significantly elevated in patients with AD compared with the other groups. Applied as single markers, p-tau231and p-tau181 reached specificity levels greater than 75% between AD and the combined non-AD group when sensitivity was set at 85% or greater. Statistical differences between the assay performances are presented. Particularly, discrimination between AD and dementia with Lewy bodies was maximized using p-tau181at a sensitivity of 94% and a specificity of 64%, and p-tau231 maximized group separation between AD and frontotemporal dementia with a sensitivity of 88% and a specificity of 92%. Combinations of the 3 markers did not add discriminative power compared with the application as single markers. CONCLUSIONS: The p-tau proteins in CSF come closest to fulfilling the criteria of a biological marker of AD. There is a tendency for p-tau proteins to perform differently in the discrimination of primary dementia disorders from AD.

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PubMed2004

Molecular evolution and genetics of the Saitohin gene and tau haplotype in Alzheimer's disease and argyrophilic grain disease.

A single nucleotide polymorphism that results in an amino acid change (Q7R) has been identified in the Saitohin (STH) gene and was initially found to be over-represented in the homozygous state in subjects with late-onset Alzheimer's disease (AD). More extensive studies provide limited support for the association with AD, but confirm an association of the Q allele with progressive supranuclear palsy and argyrophilic grain disease. A homologous sequence was found in the appropriate location of the rat and mouse tau genes, but there was no open reading frame allowing STH expression in these species, suggesting relatively recent evolution of this gene. In some non-human primates, the STH gene was identified, and this was found to differ from the human gene at two of 128 amino acids. All primates in which the STH gene was identified were homozygous for the R allele of STH, suggesting this is the ancestral allele. This observation was surprising, in that the Q allele is more common in human populations, and raises the possibility that natural selection has operated to favor individuals carrying this allele. The STH polymorphism is part of the tau gene haplotype, of which two major variants exist in human populations, the Q being part of the H1 haplotype and the R part of the H2 haplotype. More detailed studies confirm the H2 haplotype to be the ancestral tau gene. This situation is reminiscent of the evolution of the apolipoprotein (ApoE) gene, another locus that is potentially important for the risk of development of AD.

Aged↗
PubMed2004

Aging, gender and APOE isotype modulate metabolism of Alzheimer's Abeta peptides and F-isoprostanes in the absence of detectable amyloid deposits.

Aging and apolipoprotein E (APOE) isoform are among the most consistent risks for the development of Alzheimer's disease (AD). Metabolic factors that modulate risk have been elusive, though oxidative reactions and their by-products have been implicated in human AD and in transgenic mice with overt histological amyloidosis. We investigated the relationship between the levels of endogenous murine amyloid beta (Abeta) peptides and the levels of a marker of oxidation in mice that never develop histological amyloidosis [i.e. APOE knockout (KO) mice with or without transgenic human APOEepsilon3 or human APOEepsilon4 alleles]. Aging-, gender-, and APOE-genotype-dependent changes were observed for endogenous mouse brain Abeta40 and Abeta42 peptides. Levels of the oxidized lipid F2-isoprostane (F2-isoPs) in the brains of the same animals as those used for the Abeta analyses revealed aging- and gender-dependent changes in APOE KO and in human APOEepsilon4 transgenic KO mice. Human APOEepsilon3 transgenic KO mice did not exhibit aging- or gender-dependent increases in F2-isoPs. In general, the changes in the levels of brain F2-isoPs in mice according to age, gender, and APOE genotype mirrored the changes in brain Abeta levels, which, in turn, paralleled known trends in the risk for human AD. These data indicate that there exists an aging-dependent, APOE-genotype-sensitive rise in murine brain Abeta levels despite the apparent inability of the peptide to form histologically detectable amyloid. Human APOEepsilon3, but not human APOEepsilon4, can apparently prevent the aging-dependent rise in murine brain Abeta levels, consistent with the relative risk for AD associated with these genotypes. The fidelity of the brain Abeta/F2-isoP relationship across multiple relevant variables supports the hypothesis that oxidized lipids play a role in AD pathogenesis, as has been suggested by recent evidence that F2-isoPs can stimulate Abeta generation and aggregation.

Aging↗
PubMed2004

Induction of hyperphosphorylated tau in primary rat cortical neuron cultures mediated by oxidative stress and glycogen synthase kinase-3.

Neurofibrillary tangles (NFT) containing paired helical filaments (PHF) composed of abnormally phosphorylated tau are one of the hallmark lesions of the Alzheimer's disease (AD) brain. Although phosphorylation of tau is thought to precede the formation of PHF, the kinases/phosphatases involved remain poorly understood. Here we report that treatment of primary rat cortical neuron cultures with cuprizone, a copper chelator, in combination with oxidative stress (Fe(2+)/H(2)O(2)), significantly increased aberrant tau phosphorylation identified by TG3 immunochemistry. To determine the potential contribution of glycogen synthase kinase-3 (GSK-3) to the phosphorylation of tau in this model, activity of GSK-3 was determined. Cultures treated with cuprizone/Fe(2+)/H(2)O(2) showed significantly increased GSK-3 activity compared with control cultures or cultures treated with cuprizone, or Fe(2+)/H(2)O(2) alone. Concomitant treatment of cultures with lithium, a GSK-3 inhibitor, significantly decreased GSK-3 activity and reduced TG3 staining. Together these data suggest a culture model of hyperphosphorylated tau that implicates increased GSK-3 activity.

Animals↗