Glucose hypometabolism and neuropathological correlates in brains of dementia with Lewy bodies

Cerebral glucose metabolism using positron emission tomography (PET) with (18)F-fluorodeoxyglucose was examined in 11 patients with probable Alzheimer's disease (AD), 6 patients with probable, and 1 patient with autopsy-confirmed dementia with Lewy bodies (DLB) as well as in 10 age-matched normal control subjects. Among widespread cortical regions showing glucose hypometabolism in the DLB group, the metabolic reduction was most pronounced in the visual association cortex compared to that in the AD group. Using a metabolic ratio of 0.92 in the visual association cortex as a cutoff (mean-2 SD of normal control subjects), DLB could be distinguished from AD with a sensitivity of 86% and a specificity of 91%. In contrast, apolipoprotein E4 allele frequency and cerebrospinal fluid tau levels did not differ significantly between the two groups. In order to further dissect out neuropathological correlates of the dysfunctional occipital lobe, postmortem brains from 19 patients with AD and 17 with DLB as well as 11 brains from normal controls were examined. A distinct and extensive spongiform change with coexisting gliosis was variably noted throughout cerebral white matter with relative sparing of gray matter in DLB. Notably, the white matter spongiform change and gliosis was most prominently and consistently found in the occipital region of DLB, and the severity of the spongiform change in each brain region generally paralleled to the regional difference in reduced glucose metabolism between the living AD and DLB patients. These findings suggest that (1) among several potential antemortem biomarkers in the diagnosis of DLB, measures of the glucose metabolism in the occipital cortex may be an informative diagnostic aid to distinguish DLB from AD; and (2) a pathological process that generates widespread spongiform change and gliosis in long projection fibers may contribute, at least in part, to the characteristic imaging features of DLB.

Interaction of aluminum with PHFtau in Alzheimer's disease neurofibrillary degeneration evidenced by desferrioxamine-assisted chelating autoclave method

To demonstrate that aluminum III (Al) interacts with PHFtau in neurofibrillary degeneration (NFD) of Alzheimer's disease (AD) brain, we developed a "chelating autoclave method" that allows Al chelation by using trivalent-cationic chelator desferrioxamine. Its application to AD brain sections before Morin histochemistry for Al attenuated the positive fluorescence of neurofibrillary tangles, indicating Al removal from them. This method, applied for immunostaining with phosphorylation-dependent anti-tau antibodies, significantly enhanced the PHFtau immunoreactivity of the NFD. These results suggest that each of the phosphorylated epitopes in PHFtau are partially masked by Al binding. Incubation of AD sections with AlCl(3) before Morin staining revealed Al accumulation with association to neurofibrillary tangles. Such incubation before immunostaining with the phosphorylation-dependent anti-tau antibodies abolished the immunolabeling of the NFD and this abolition was reversed by the Al chelation. These findings indicate cumulative Al binding to and thereby antigenic masking of the phosphorylated epitopes of PHFtau. Al binding was further documented for electrophoretically-resolved PHFtau on immunoblots, indicating direct Al binding to PHFtau. In vitro aggregation by AlCl(3) was observed for PHFtau but was lost on dephosphorylation of PHFtau. Taken together, phosphorylation-dependent and direct PHFtau-Al interaction occurs in the NFD of the AD brain.

Urocortin expression in the human central nervous system

OBJECTIVE AND STUDY DESIGN

Urocortin is a recently identified neuropeptide of the corticotrophin-releasing factor (CRF) family in the mammalian brain and has been demonstrated to stimulate ACTH secretion from pituitary cells, but its expression in human brain tissue including the hypothalamus has not been examined. In this study, we first examined urocortin expression in the hypothalamus (20 cases) and pituitary stalks (17 cases) of human brain obtained from autopsy using immunohistochemistry and mRNA in situ hybridization.

RESULTS

Neither urocortin immunoreactivity nor mRNA hybridization signals were detected in the hypothalami and pituitary stalks while CRF immunoreactivity was detected in the paraventricular nuclei of the hypothalami in 10/20 cases and in nerve fibres of the stalks in 17/17 cases. These results indicate that urocortin does not act on the hypothalamo-pituitary-adrenal axis, at least not in the same manner as CRF in humans. We then examined urocortin expression in various portions of the brain in 7 cases. Both urocortin immunoreactivity and mRNA hybridization were detected in Purkinje cells of the cerebellum and anterior horn cells of the spinal cord in specimens examined. Urocortin expression was, however, variably seen in superior olivary nuclei (two out of six cases examined) and in the Edingar-Westphal nuclei (one out of three cases examined).

CONCLUSIONS

The distribution of urocortin in the human central nervous system suggests that urocortin may work as a neurotransmitter like other neuropeptides in the human.

Codon 219 Lys allele of PRNP is not found in sporadic Creutzfeldt-Jakob disease

The polymorphism at codon 219 of the prion protein gene (PRNP) was found in the general Japanese population with 6% allele frequency. Herein, we examined 85 cases of sporadic Creutzfeldt-Jakob disease (CJD) for the codon 219 polymorphism. The codon 219Glu/Lys heterozygous polymorphism was not found in these CJD cases. In addition, we examined 43 patients with dementia of non-CJD origin, and 4 were found to have the codon 219Glu/Lys heterozygous polymorphism with a similar allele frequency as in the general population. Thus, the codon 219Glu/Lys heterozygous polymorphism might be uniquely excluded from sporadic CJD.

Amyloid beta-protein (Abeta) 1-40 but not Abeta1-42 contributes to the experimental formation of Alzheimer disease amyloid fibrils in rat brain

Two major C-terminal variants ending at Val40 and Ala42 constitute the majority of amyloid beta-protein (Abeta), which undergoes postsecretory aggregation and deposition in the Alzheimer disease (AD) brain. To probe the differential pathobiology of the two Abeta variants, we used an in vivo paradigm in which freshly solubilized Abeta1-40 or Abeta1-42 was injected into rat brains, followed by examination using Congo red birefringence, Abeta immunohistochemistry, and electron microscopy. In the rat brain, soluble Abeta 1-40 and Abeta1-42 formed aggregates, and the Abeta1-40 but not the Abeta1-42 aggregates showed Congo red birefringence. Electron microscopy revealed that the Abeta1-40 aggregates contained fibrillar structures similar to the amyloid fibrils of AD, whereas the Abeta1-42 aggregates contained nonfibrillar amorphous material. Preincubation of Abeta1-42 solution in vitro led to the formation of birefringent aggregates, and after injection of the preincubated Abeta1-42, the aggregates remained birefringent in the rat brain. Thus, a factor or factors might exist in the rat brain that inhibit the fibrillar assembly of soluble Abeta1-42. To analyze the postsecretory processing of Abeta, we used the same in vivo paradigm and showed that Abeta1-40 and Abeta1-42 were processed at their N termini to yield variants starting at pyroglutamate, and at their C termini to yield variants ending at Val40 and at Val39. Thus the normal rat brain could produce enzymes that mediate the conversion of Abeta 1-40/1-42 into processed variants similar to those in AD. This experimental paradigm may facilitate efforts to elucidate mechanisms of Abeta deposition evolving into amyloid plaques in AD.

Urocortin expression in human pituitary gland and pituitary adenoma

Urocortin is a recently identified neuropeptide of the CRF family in the mammalian brain, but its expression in human tissue has been little studied. In this study, we examined urocortin expression in human anterior pituitary gland and pituitary adenomas by RIA, high performance liquid chromatography, immunohistochemistry, messenger ribonucleic acid (mRNA) in situ hybridization, and reverse transcriptase-PCR. Immunoreactive urocortin concentrations in normal pituitary tissue extract were 103.25 +/- 39.05 ng/g wet wt (mean +/- SEM; n = 4), and their levels were all significantly higher than those in other portions of central nervous system of the same subjects. High performance liquid chromatography analysis of human pituitary extract demonstrated a single peak corresponding to that of the expected chromatographic mobility of synthetic human urocortin-(1-40). Urocortin-immunoreactive cells were detected in the anterior pituitary gland. Neither urocortin-immunoreactive nerve fibers nor cells were detected in the posterior lobe. Immunostaining in serial mirror tissue sections revealed that 76.55 +/- 3.06% of urocortin-immunoreactive cells expressed GH immunoreactivity, whereas 22.25 +/- 3.02% and less than 1% of urocortin-immunoreactive cells expressed PRL and ACTH, respectively. mRNA hybridization signals of urocortin were also detected in urocortin-immunopositive pituitary cells. The reverse transcriptase-PCR analysis demonstrated a 145-bp RNA band corresponding to that of the expected length of urocortin in all cases of normal pituitary glands examined (n = 3). We also immunostained urocortin in 52 cases of human anterior pituitary adenomas, including GH-producing adenomas (n = 14), ACTH-producing adenomas (n = 13), PRL-producing adenomas (n = 11), and nonfunctioning hormonally inactive adenomas (n = 14). No urocortin immunoreactivity was detected in these adenoma cells, except for one case of GH-producing adenoma and one case of nonfunctioning adenoma. We also performed mRNA in situ hybridization in 27 adenomas. No hybridization signals were detected in these adenomas, except in two cases. The results described above indicated that urocortin is synthesized in human anterior pituitary cells and may play an important role in biological features of normal pituitary gland, possibly as an autocrine or a paracrine regulator

Interaction of aluminum with paired helical filament tau is involved in neurofibrillary pathology of Alzheimer's disease

Since the first reports of aluminum-induced neurofibrillary degeneration in experimental animals, extensive studies have been performed to clarify the role played by aluminum in the pathogenesis of Alzheimer's disease (AD). Additional evidence implicating aluminum in AD includes elevated levels of aluminum in the AD brain, epidemiologic data linking aluminum exposure to AD, and interactions between aluminum and protein components in the pathologic lesions of AD, i.e., neurofibrillary tangles (NFTs) and senile plaques. As most of this evidence is circumstantial and some of it is not consistent in all reports, the role of aluminum in the pathogenesis of AD has remained controversial. However, the interaction of aluminum with altered forms of tau in the paired helical filaments (PHFs) of neurofibrillary lesions is highly likely to contribute to the formation of NFTs because (1) aluminum and abnormally phosphorylated tau (known as PHF tau) are colocalized in NFTs, and (2) aluminum is known to preferentially interact with such phosphorylated proteins. Recently, it was demonstrated that aluminum binds selectively to PHF tau, induces PHF tau to aggregate, and retards the in vivo proteolysis of PHF tau. These data suggest that aluminum could serve as a cofactor in the formation of NFTs by interacting with PHF tau. This review summarizes the current understanding of how aluminum might contribute to the formation of neurofibrillary lesions from PHF tau in neurons of the AD brain.

Humanized prion protein knock-in by Cre-induced site-specific recombination in the mouse

To establish humanized mice with a knock-in (gene replacement) technique, we constructed a targeting vector which consists of the human prion protein and the loxP sequences. The introduced human prion protein with the loxP system in the embryonic stem cells was transmitted through the mouse germ line. Transient expression of Cre recombinase in the fertilized eggs resulted in the prion protein humanized mice. The Cre-loxP-mediated gene replacement is a simple and efficient method which is generally applicable to make humanized animal models.

Paired helical filament tau (PHFtau) in Niemann-Pick type C disease is similar to PHFtau in Alzheimer's disease

Niemann-Pick Type C disease (NPC) is a cholesterol storage disease with defects in the intracellular trafficking of exogenous cholesterol derived from low density lipoproteins. In NPC cases with a chronic progressive course, neurofibrillary tangles (NFTs) that consist of paired helical filaments (PHFs) have been reported. To determine if NPC tangles contain abnormal tau proteins (known as PHFtau) similar to those found in Alzheimer's disease (AD) tangles, we examined the brains of five NPC cases by immunohistochemical and Western blot methods using a library of antibodies to defined epitopes of PHFtau. We show here that PHFtau in tangle-rich NPC brains is indistinguishable from PHFtau in AD brains. We speculate, that the generation of PHFtau in NPC may induce a cascade of pathological events that contribute to the widespread degeneration of neurons, and that these events may be similar in NPC and AD.

Neurofibrillary pathology and aluminum in Alzheimer's disease

Since the first reports of aluminum-induced neurofibrillary degeneration in experimental animals, extensive studies have been performed to clarify the role played by aluminum in the pathogenesis of Alzheimer's disease (AD). Additional evidence implicating aluminum in AD includes elevated levels of aluminum in the AD brain, epidemiological data linking aluminum exposure to AD, and interactions between aluminum and protein components in the pathological lesions of AD, i.e., neurofibrillary tangles (NFTs) and senile plaques (SPs). As most of this evidence is circumstantial and some of it is not consistent in all reports, the role of aluminum in the pathogenesis of AD has remained controversial. However, the interaction of aluminum with altered forms of tau in the paired helical filaments (PHFs) of neurofibrillary lesions is highly likely to contribute to the formation of NFTs because (1) aluminum and abnormally phosphorylated tau (known as PHF tau) are colocalized in NFTs, and (2) aluminum is known to preferentially interact with such phosphorylated proteins. Recently, we demonstrated that aluminum binds selectively to PHF tau, induces PHF tau to aggregate, and retards the in vivo proteolysis of PHF tau. These data suggest that aluminum could serve as cofactor in the formation of NFTs by interacting with PHF tau. This review summarizes current understanding of how aluminum might contribute to the formation of neurofibrillary lesions from PHF tau in neurons of the AD brain.

Aluminum modifies the properties of Alzheimer's disease PHF tau proteins in vivo and in vitro

Hyperphosphorylated adult human CNS tau (PHF tau or A68) forms paired helical filaments (PHFs) in neurofibrillary tangles (NFTs), neuropil threads, and dystrophic neurites associated with senile plaques (SPs) during the progression of Alzheimer's disease (AD). While amyloid fibrils in SPs are composed of beta-amyloid (A beta), NFTs and SPs contain similar associated components such as ubiquitin, alpha 1-antichymotrypsin (ACT), apolipoprotein E (ApoE), heparan sulfate proteoglycans (HSPGs), and aluminum salts. Thus, SPs and NFTs may result from specific interactions between PHF tau, A beta, and these other components. In fact, intracerebral injections of PHF tau induce co-deposits of A beta, ACT, and ubiquitin (Shin et al., 1993). To examine this issue further, we probed interactions between PHF tau, aluminum salts, and other plaque and tangle components. We investigated in vivo interactions of PHF tau and aluminum chloride (AlCl3) with other plaque and tangle components by injecting PHF tau with and without AlCl3 into the rodent brain. PHF tau co-injected with AlCl3 formed aggregates that persisted much longer in the rat brain, and induced longer-lived co-deposits of A beta, ubiquitin, ACT, and ApoE than PHF tau alone. Injections of PHF tau with AlCl3 also induced neurons near the injection site to acquire PHF tau-like properties as monitored with antibodies (AT8, T3P, PHF1) that recognize defined PHF tau epitopes containing phosphoserine residues (Ser202, Ser396, Ser404). Injections of AlCl3 alone as well as injections of normal adult and fetal CNS tau, several different synthetic peptides, neurofilament proteins, ACT, HSPGs, or ApoE with and without AlCl3 failed to induce co-deposits of A beta or alter the immunoreactivity of tau in rodent neurons. To determine if aluminum salts interact directly and specifically with PHF tau in situ, we pretreated sections of AD hippocampus with 10 mM AlCl3 and then probed these sections by immunohistochemistry with antibodies to PHF tau as well as to a number of other plaque and tangle components. Preincubation of these sections with AlCl3 diminished PHF tau immunoreactivity in NFTs and SPs using the PHF tau-specific antibodies AT8, T3P, and PHF1, while the immunoreactivity of other plaque and tangle proteins (A beta, ubiquitin, ACT, HSPGs, ApoE) was not abolished. We also examined the effects of AlCl3 on PHF tau and normal adult human CNS tau in vitro. AlCl3 had no effect on normal adult human CNS tau, while increasing concentrations of AlCl3 (from 0.1 to 1.0 mM) induced PHF tau to aggregate at the top of the stacking gel, and at high concentrations (0.3 and 1.0 mM) of AlCl3, PHF tau completely failed to enter the gel. These studies suggest that aluminum binds to PHF tau, induces these proteins to aggregate, and retards their proteolysis. Further, since intracerebral injections of PHF tau with and without AlCl3 in rats appear uniquely capable of inducing co-deposits of a number of proteins found in authentic AD SPs and NFTs (including A beta, ubiquitin, ACT, and ApoE), we speculate that the contributions of PHF tau to plaque and tangle formation in AD may be modulated by aluminum.

Biopsy-derived adult human brain tau is phosphorylated at many of the same sites as Alzheimer's disease paired helical filament tau

Tau from Alzheimer's disease (AD) paired helical filaments (PHF-tau) is phosphorylated at sites not found in autopsy-derived adult tau from normal human brains, and this suggested that PHF-tau is abnormally phosphorylated. To explore this hypothesis, we examined human adult tau from brain biopsies and demonstrated that biopsy-derived tau is phosphorylated at most sites thought to be abnormally phosphorylated in PHF-tau. These sites also were phosphorylated in autopsy-derived human fetal tau and rapidly processed rat tau. The hypophosphorylation of autopsy-derived adult human tau is due to rapid dephosphorylation postmortem, and protein phosphatases 2A (PP2A) and 2B (PP2B) in human brain biopsies dephosphorylate tau in a site-specific manner. The down-regulation of phosphatases (i.e., PP2A and PP2B) in the AD brain could lead to the generation of maximally phosphorylated PHF-tau that does not bind microtubules and aggregates as PHFs in neurofibrillary tangles and dystrophic neurites.

Widespread distribution of tau in the astrocytic elements of glial tumors

Recently tau immunoreactivity has been observed in astrocytes in Alzheimer's disease and other neurological diseases. We examined the immunohistochemical localization of tau in 110 human brain tumors. Tau was widely distributed in the glial neoplastic cells and the reactive astrocytes in tumor tissues. In human surgical specimens positive immunostaining for tau was frequently observed in astrocytic tumors, oligodendroglial tumors, and glioblastoma, as well as neuronal tumors. The astrocytic neoplastic cells in medulloblastoma and other poorly differentiated tumors were also stained. In contrast, no immunoreactivity was observed in meningiomas and schwannomas. The expression of tau in brain tumors was mainly restricted to those cells with astrocytic features rather than small immature cells. The expression of tau mRNA was also demonstrated in astrocytic tumors. In conjunction with the findings of tau-positive astrocytes in some degenerative disorders, astrocytes are considered to have a potential to express tau through neoplastic transformation and reactive processes.

Alzheimer disease A68 proteins injected into rat brain induce codeposits of beta-amyloid, ubiquitin, and alpha 1-antichymotrypsin

Aberrantly phosphorylated tau proteins (i.e., A68 or PHF-tau) and beta-amyloid or A4 (beta A4) peptides are major components of pathologic lesions in Alzheimer disease (AD). Although A68 and beta A4 colocalize in AD neurofibrillary tangles (NFTs) and amyloid-rich senile plaques (SPs), the mechanisms leading to the convergence of A68, beta A4, and other proteins in the same AD lesions are unknown. To probe the biological properties of A68 in vivo, and to assess interactions of A68 with endogenous proteins in the rodent brain, we injected A68, dephosphorylated A68 (DEP-A68), and normal adult human tau protein into the hippocampus and neocortex of rats. In marked contrast to DEP-A68 and tau, A68 resisted rapid proteolysis and induced codeposits of three rodent proteins--i.e., beta A4, ubiquitin, and alpha 1-antichymotrypsin (ACT)--that accumulate in AD NFTs and SPs together with A68. These findings suggest that A68 may interact with beta A4, ubiquitin, and ACT in neuronal perikarya as well as in the extracellular space after release of A68 from degenerating neurons. The model system described here will facilitate efforts to elucidate mechanisms leading to the convergence of A68, beta A4, ubiquitin, and ACT in hallmark lesions of AD.

Altered tau and neurofilament proteins in neuro-degenerative diseases: diagnostic implications for Alzheimer's disease and Lewy body dementias

The neuronal cytoskeleton is one of the most profoundly altered organelles in late life neuro-degenerative disorders that are characterized by progressive impairments in cognitive abilities. The elucidation of the protein building blocks of these organelles as well as advances in understanding how these proteins become altered in Alzheimer's disease (AD) and other less common dementing illnesses, i.e., diffuse Lewy body disease (DLBD) or the Lewy body variant of AD (LBVAD), will provide insights into the molecular basis of these disorders. Within, we review evidence that normal adult human tau is abnormally phosphorylated and converted into the subunits of AD paired helical filaments (PHFs), and that Lewy bodies (LBs) represent accumulation of altered neurofilament (NF) triplet subunits. Although the precise biological consequences of PHF and LB formation in neurons is unknown, growing evidence suggests that the formation of PHFs and LBs from normal neuronal cytoskeletal proteins could have deleterious effects on neuronal function and survival. Finally, insights into the composition of PHFs and LBs could lead to the development of novel strategies for the timely and accurate diagnosis of AD, DLBD and the LBVAD.

Abnormal isoform of prion proteins accumulates in the synaptic structures of the central nervous system in patients with Creutzfeldt-Jakob disease

A new method, which enabled the first immunohistochemical documentation of abnormal prion protein (PrP) in all patients with Creutzfeldt-Jakob disease (CJD), was established. This method designated as "hydrolytic autoclaving" revealed punctate PrPCJD stainings around the neuronal cell bodies and dendrites in CJD brains. These punctate stainings were almost identical with that of synaptophysin, suggesting PrPCJD accumulations in the synaptic structures. Subcellular fractionation revealed that prion protein in Creutzfeldt-Jakob disease (PrPCJD) was most concentrated in the synaptosomal fraction. In CJD patients with a long clinical course, synaptophysin immunoreactivity decreased, and synaptic PrPCJD accumulated with a wider distribution. These results suggest that synaptic PrPCJD accumulations might be responsible for the neuronal dysfunction and degeneration in CJD.

Massive accumulation of modified tau and severe depletion of normal tau characterize the cerebral cortex and white matter of Alzheimer's disease. Demonstration using the hydrated autoclaving method

Using the hydrated autoclaving method, a new immunohistochemical procedure to enhance tau immunoreactivity in formalin-fixed brain tissue, the authors recently reported that tau protein is detected in neuronal cell bodies and proximal dendrites, gray matter neuropil, axons, and glial cells in normal human hippocampus and neocortex. In the this study, the authors performed a comparative study of the distribution of normal and modified forms of tau in Alzheimer's disease (AD) and control brains. In the cerebral cortex and white matter of AD brains, a massive accumulation of modified tau and/or severe depletion of normal tau were documented in all the tau compartments. In mild AD cases, gray matter neuropil, axons, and glial cells were less severely involved than neuronal perikarya. In the controls, neuronal perikarya were often involved by modified tau accumulation, but the other compartments showed normal distribution. These observations suggest that modifications of tau which lead to neurofibrillary lesions in AD may begin in neuronal perikarya and extend to the other tau compartments in advanced stages of the disease.

Chordoma in early childhood: a clinicopathological study

A case of clival chordoma in a 4-year-old girl is presented. The tumor regrew rapidly after it was partially removed, and the patient died after a clinical course of 11 months. An autopsy revealed a massive clival mass and widespread metastases in the dura mater, skull bone, bilateral lungs, liver, sternum, left humerus, and vertebrae. Pathological findings showed that the tumor cells were poorly differentiated, with a rare, but typical, physaliphorous appearance. The presence of epithelial differentiation proteins, mitochondria surrounded by rough endoplasmic reticulum, and desmosomes was demonstrated in the tumor cells both immunohistochemically and ultrastructurally. Thus, the tumor was diagnosed as a chordoma. The literature pertaining to intracranial chordoma in early childhood is reviewed. Rapid growth and distant metastases may occur in chordomas at a young age.

Hydrated autoclave pretreatment enhances tau immunoreactivity in formalin-fixed normal and Alzheimer's disease brain tissues

We developed a new immunohistochemical method by which normal tau antigenicity can be visualized in paraffin sections of formalin-fixed brain tissue. This method consists of autoclave pretreatment of sections immersed into distilled water (hydrated autoclaving) before incubation with anti-tau antibodies. In normal human brain, immunoreactive tau was detected in neuronal cell bodies and dendrites, axon fibers, astroglia, oligodendroglia and gray matter neuropil. In previous studies on normal tau distribution, different optimized fixations that effectively preserve tau antigenicity were used but none of these revealed all of these compartments together. Our method is therefore considered to be more sensitive for detecting normal tau immunoreactivity. In addition, hydrated autoclaving had an enhancing effect on the abnormally phosphorylated (modified) tau immunoreactivity in formalin-fixed brains. In hydrated autoclaving of sections from patients with Alzheimer's disease, neuropil threads, senile plaques, extracellular and intracellular tangles were enhanced in quantity and in staining intensity. Therefore, modified tau appears to accumulate more densely than expected from conventional immunohistochemistry. Immunoblot analysis showed that normal or modified tau immunoreactivity was totally or partially eliminated on formalin treatment and could be revisualized by hydrated autoclaving, an event presumably related to recovering of formalin-masked tau antigens through denaturation by hydrated autoclaving.

Modified tau is present in younger nondemented persons: a study of subcortical nuclei in Alzheimer's disease and progressive supranuclear palsy

Tau-positive neurons relating to neurofibrillary tangles and diffuse cytoplasmic stainings were quantitatively examined in the brains of 61 nondemented persons including 24 age-matched controls, 10 patients with Alzheimer's disease (AD) and 5 with progressive supranuclear palsy (PSP). In nondemented persons, the locus ceruleus (LC) was found to contain tau-positive neurons initially in persons in their 30s, whereas the hippocampus contained such neurons initially in persons in their 40s. The LC had a higher incidence and density than the hippocampus in almost all age classes. As neuronal tau accumulation is considered a histological change occurring with normal aging, the LC might be involved in the earliest aging in the normal brain. In AD there was conspicuous tau accumulation in the same sites which were vulnerable to tau accumulation in the age-matched controls. In PSP tau accumulated heavily in a set of sites different from the age-matched controls and AD. Thus, subcortical tau accumulation in AD is increased far more than that under normal aging process, while that in PSP is not simply in an increased state of the normal aging process.

Increased senile plaques without microglia in Alzheimer's disease

To clarify the association of microglia with senile plaques, the brains from 13 patients with Alzheimer's disease (AD) and 23 nondemented aged controls were investigated immunohistochemically by a double-labeling method using anti-beta-protein antiserum and anti-ferritin antibody, which is a recently reported microglia marker. In addition, a quantitative analysis was performed. The senile plaques which appeared initially in the nondemented aged controls consisted of a diffuse type without any amyloid cores and these were found in the group aged 50-59 years. The great majority of them were found to contain no ferritin-positive microglia. The number and proportion (percentage) of microglia-containing diffuse plaques increased with age. Classical and compact plaques began to appear in the brains of the group aged 70 years and over, and practically all of them contained microglia. These results suggest that microglia are not associated with initial plaque formation, but correlate with amyloid core formation. In AD, the most prominent feature was that the diffuse plaques, which contained either no or only a few ferritin-positive microglia, increased markedly.

Increased tau accumulation in senile plaques as a hallmark in Alzheimer's disease

To identify the tau component in senile or kuru plaques, the authors examined brain sections from 12 patients with Alzheimer's disease (AD), 6 with Creutzfeldt-Jakob disease (CJD), and 20 nondemented aged controls using anti-beta protein, anti-buman prion protein, and affinity-purified tau-specific antibody. The tau component was identified both in senile and kuru plaques. In AD, tau-positive senile plaques were found in all cerebral cortices of almost all cases, and the tau-positivity of plaques in cerebral cortices was 5.1 to 27.5%. In CJD, tau-positive senile and kuru plaques were restricted to the hippocampus, and the tau-positivity was 4.3 and 1.2%, respectively. In nondemented aged controls, tau-positive senile plaques also were restricted mostly to the hippocampus, and the tau-positivity was 1.3%. Significant differences in the tau-positivity of senile plaques were found between AD and CJD and nondemented aged controls, and no significant differences were found between CJD and nondemented aged controls. These observations are important because increased tau accumulation in senile plaques can be a hallmark of AD.