Transforming growth factor-betas in neurodegenerative disease

Transforming growth factors-betas (TGF-betas), a family of multifunctional peptide growth factors, affect cells of the central nervous system (CNS). The three mammalian TGF-beta isoforms, TGF-betas 1, 2 and 3, are expressed in adult human brain. Since neuronal degeneration is a defining feature of CNS degenerative diseases, TGF-beta may be important because it can influence neuronal survival. In vitro TGF-beta promotes survival of rat spinal cord motoneurons and dopaminergic neurons. In addition to direct effects on neuronal survival, TGF-beta treatment of cultured astrocytes induces a reactive phenotype. Thus, TGF-beta may also normalize the extracellular matrix environment in degenerative diseases. The expression of TGF-betas change in response to neuronal injury. TGF-beta 1 expression increases in astrocytes and microglia in animal models of cerebral ischemia, while TGF-beta 2 expression increases in activated astroglial cells in human neurodegenerative diseases. TGF-betas protect neurons from a variety of insults. TGF-beta maintains survival of chick telencephalic neurons made hypoxic by treatment with cyanide and decreases the area of infarction when administered in animal models of cerebral ischemia. In vitro TGF-beta protects neurons from damage induced by treatment with beta-amyloid peptide, FeSO4 (induces production of reactive oxygen species), Ca2+ ionophores, glutamate, glutamate receptor agonists and MPTP (toxic for dopaminergic neurons). TGF-beta maintains mitochondrial potential and Ca2+ homeostasis and inhibits apoptosis in neurons. TGF-beta does not prevent neuronal degeneration in a rat model of Parkinson's disease and has yet to be tested in newly developed transgenic mouse models of Alzheimer's disease. TGF-beta is a potent neuroprotective agent which may affect the pathogenesis of neurodegenerative diseases of the CNS.

Alzheimer's disease, Lewy body disease and aging: a comparative study of the perforant pathway

The relationship between Alzheimer's disease (AD) and Lewy body disease (LBD) is poorly understood. In AD there is severe loss of neurons comprising the perforant pathway. To assess perforant pathway integrity in pure LBD we compared neuronal counts in layer II of the entorhinal cortex (ERC) in 11 cases of pure LBD that did not meet CERAD pathologic criteria for AD with ERC neuronal counts from seven AD cases with a similar disease duration and six cognitively normal individuals. We counted cell bodies/island in layer II of the ERC using formalin-fixed, paraffin-embedded, tau/cresyl violet-stained sections at the level of the rostral-most body of the hippocampus. There was marked variability in neuronal counts among cases in the LBD group; LBD data overlapped with data from both normal and AD groups. Overall, perforant pathway perikaryal counts in LBD differed significantly from those in AD, but not from those in aged normals (mean perikarya/island = 30.09 +/- 8.95, 7.57 +/- 6.08, and 38.83 +/- 8.98, respectively; F = 26.131, P < 0.001). The percent of remaining neurons bearing neurofibrillary tangles in LBD also overlapped with AD and control groups (16.17 = 13.85%, 87.86 +/- 11.81%, and 24.36 +/- 13.30% of remaining neurons, respectively, F = 65.62, P < 0.001). We conclude that although perforant pathway neuronal loss may occur in LBD, it is more often milder and more variable than that seen in AD.

Apolipoprotein E-epsilon 2 and Alzheimer's disease: genotype influences pathologic phenotype

To determine whether apolipoprotein E epsilon 2 (APOE-epsilon 2) affects neuropathology in aging and Alzheimer's disease (AD), we compared beta-amyloid plaque (A beta P) and neurofibrillary tangle densities, neuropil thread formation, and amyloid angiopathy in five APOE-epsilon 2/3 AD patients, five APOE-epsilon 3/3 AD patients, five APOE-epsilon control patients, and five APOE-epsilon 3/3 control patients. We examined the (frontal and parietal) neocortex, hippocampus, entorhinal cortex, and cerebellum and found A beta P densities to be lower (t = 3.121, p = 0.011) in the cortex of APOE-epsilon 2/3 AD patients than in APOE-epsilon 3/3 AD patients. Amyloid angiopathy was also less in APOE-epsilon 2/3 patients than in APOE-3/3 patients (U = 4.500, p = 0.027). Control APOE-epsilon 2/3 brains had little AD-related pathology; even our 102-year-old control case showed few A beta Ps compared with the elderly APOE-epsilon 3/3 cases. The APOE-epsilon 2/3 genotype may influence pathologic phenotype in some aged normal and AD populations.

Inducible nitric oxide synthase in tangle-bearing neurons of patients with Alzheimer's disease

In Alzheimer's disease (AD), affected neurons accumulate beta amyloid protein, components of which can induce mouse microglia to express the high-output isoform of nitric oxide synthase (NOS2) in vitro. Products of NOS2 can be neurotoxic. In mice, NOS2 is normally suppressed by transforming growth factor beta 1 (TGF-beta 1). Expression of TGF-beta 1 is decreased in brains from AD patients, a situation that might be permissive for accumulation of NOS2. Accordingly, we investigated the expression of NOS2 in patients with AD, using three monospecific antibodies: a previously described polyclonal and two new monoclonal antibodies. Neurofibrillary tangle-bearing neurons and neuropil threads contained NOS2 in brains from each of 11 AD patients ranging in age from 47 to 81 years. NOS2 was undetectable in brains from 6 control subjects aged 23-72 years, but was expressed in small amounts in 3 control subjects aged 77-87 years. Thus, human neurons can express NOS2 in vivo. The high-output pathway of NO production may contribute to pathogenesis in AD.

Familial and sporadic Alzheimer's disease: neuropathology cannot exclude a final common pathway

Whether all etiologic forms of Alzheimer's disease (AD) share a final common pathway is a major issue. We determined the severity and regional distribution of neuronal loss, amyloid plaques, neuritic plaques (NPs), and neurofibrillary tangles (NFTs), and calculated the ratio of neuronal loss to NPs and NFTs in brains of 19 familial AD (FAD) patients with linkage to chromosome 14, six AD patients with mutations of chromosome 21 (codon 717 of the beta-amyloid percursor protein gene), and 11 sporadic AD (SAD) patients. There was no difference in the pattern of distribution of the various pathologic features or in the ratio of neuronal loss to NPs or NFTs in any AD group. However, FAD groups could be distinguished from SAD by the greater severity and the lack of influence of apolipoprotein E genotype on pathology. These differences may reflect differences in age at onset rather than different etiopathologic mechanisms. The similarity of pathologic findings in the different AD groups provides evidence for a final common pathophysiologic pathway in AD.

Transforming growth factor-beta: neuronal and glial expression in CNS degenerative diseases

We have previously shown that the brains of patients with Alzheimer's disease (AD) express transforming growth factor (TGF)-beta 2 in neurofibrillary tangle (NFT)-bearing neurons and reactive astrocytes. The present study was undertaken to determine whether other neurodegenerative diseases were also associated with an alteration of the TGF-beta's. The immunohistochemical expression of TGF-beta 1, -2 and -3 was assessed in the brains of patients with progressive supranuclear palsy (n = 2), amyotrophic lateral sclerosis (n = 3), Lewy body disease (n = 5), Parkinson's disease (n = 1), Shy-Drager syndrome (n = 1), Pick's disease (n = 3), lobar atrophy (n = 1), and corticobasal degeneration (n = 2). Our results were compared to norms for controls (n = 8). We found expression of TGF-beta 2 in both NFT bearing neurons and tangle-bearing glial cells in progressive supranuclear palsy and in neurons with age-related NFT formation. Widespread staining of reactive astrocytes for TGF-beta 2 was observed in all degenerative diseases. TGF-beta 1 and -3 staining was not selectively altered in these diseases. We conclude that induction of TGF-beta 2 may be an intrinsic part of the processes that underlie NFT formation and reactive gliosis in a variety of neurodegenerative diseases.

Apolipoprotein E epsilon 4 allele and the lifetime risk of Alzheimer's disease. What physicians know, and what they should know

BACKGROUND

Published studies now show a clear association between Alzheimer's disease (AD) and the apolipoprotein E epsilon 4 allele (APOE* epsilon 4). The clinical value of this information to estimate a healthy individual's lifetime risk of AD has not been well delineated. Physicians dealing with AD may not know either the lifetime risk of developing AD or the effect of the APOE genotype on this risk. Because the lifetime risk of AD depends in part on life expectancy, and available figures on APOE are not population based, a computation is necessary to derive risk estimates useful to physicians.

OBJECTIVES

To estimate the lifetime risk of AD and the effect of APOE genotype information on that risk and to assess the knowledge of these risks among physicians who manage patients with dementia.

DESIGN

Estimation of risk of AD and survey of physician awareness. The lifetime risk of developing AD without APOE genotype information was first computed for 65-year-olds from existing epidemiologic studies of age-related AD incidence and an actuarial life-table analysis. Using this computed a priori risk of AD and published studies of APOE genotypes in individuals with and without AD, we used a Bayesian analysis to determine the risk of developing AD, with and without an APOE* epsilon 4 allele, for unaffected 65-year-olds. To assess physician knowledge of the lifetime risk of AD and the effect of APOE genotyping on the risk, 50 neurologists, internists, geriatricians, geriatric psychiatrists, and family physicians who manage patients with dementia were randomly selected to participate in a questionnaire-driven telephone survey.

RESULTS

In a person with no family history of AD, the epidemiologic/actuarial lifetime risk of AD is approximately 15%. Based on a Bayesian calculation and published APOE data, the lifetime risk of AD is 29% for individuals with one APOE* epsilon 4 allele and it is 9% if no APOE* epsilon 4 allele is present. Physician awareness survey results were as follows: 42% of physicians correctly estimated the approximate lifetime risk of AD; of these, only one third were moderately sure of their response. Only three physicians correctly estimated the change in risk given the APOE* epsilon 4 genotype; only one of these was at least moderately sure.

CONCLUSIONS

Determining the APOE* epsilon 4 status of healthy adults with no family history of AD approximately doubles (for the epsilon 4 allele) or reduces by 40% (for the non-epsilon 4 allele) the uninformed lifetime risk of developing AD. Even with an APOE* epsilon 4 allele, the lifetime risk remains below 30%. Most physicians managing patients with AD do not know the lifetime risk of AD, and very few know how APOE* epsilon 4 status modifies the risk. These clinically relevant risk figures should be more widely disseminated among physicians.

Altered expression of transforming growth factor-beta in Alzheimer's disease

We compared immunohistochemical expression of the transforming growth factor-betas (TGF-beta 1, TGF-beta 2, and TGF-beta 3) using brain tissue from patients with nondominantly inherited Alzheimer's disease (NDAD) (n = 9), autosomal dominantly inherited Alzheimer's disease with linkage to 14q24.3 (FAD-14) (n = 4), and cognitively normal controls (n = 10) to determine whether their pathologic changes are associated with an altered distribution of the TGF-betas. We found increased expression of TGF-beta 2 in large, tangle-bearing neurons with widespread staining of glia in NDAD and FAD-14 patients compared with control cases. This result was confirmed with sandwich ELISA assays of brain tissue, which showed TGF-beta 2 levels in AD and NDAD to average 3.2 times the average level of control cases. Despite proximity of TGF-beta 1 and TGF-beta 3 to the sites of susceptibility loci on chromosomes 19 and 14, we did not find that TGF-beta 1 and TGF-beta 3 were selectively altered in any AD subtypes. However, selective induction of TGF-beta 2 may occur in NDAD and FAD-14.

Familial Alzheimer's disease and cortical Lewy bodies: is there a genetic susceptibility factor?

The reason for the occurrence of Lewy body disease (LBD) in Alzheimer's disease (AD) patients is unknown. If brains from etiologically different AD groups differ in their tendency to develop cortical Lewy bodies, the concurrence of LBD in AD patients may be a manifestation of the AD process in specific AD subsets. To address this issue, we counted cortical Lewy bodies in AD patients with genetic abnormalities on chromosome 14 (n = 19), and chromosome 21 (n = 3), sporadic AD (n = 27), Down's syndrome (n = 1) and control (n = 26) patients. Cortical Lewy bodies were occasionally present in AD patients with long-duration disease in most of the above AD subgroups, but were not present in any of our age-matched control cases. We suggest that cortical Lewy body formation may be an intrinsic part of the late pathologic changes of AD regardless of etiology and that it is not specific to any of the AD subtypes studied.

Ki-67 immunoreactivity in Alzheimer's disease and other neurodegenerative disorders

Cell cycle-associated nuclear proteins may have more specialized functions in the adult nervous system in addition to those directly associated with cell proliferation, as suggested by a recent study showing that neurofibrillary tangles (NFT) and dystrophic neurites in Alzheimer's disease (AD) are immunoreactive for the proliferation-associated antigen p105. To further investigate this hypothesis, we studied the expression of another proliferation-associated antigen, Ki-67, in the brains of patients with AD and other neurodegenerative disorders. Formalin-fixed, paraffin-embedded sections from autopsy cases of AD, Down's syndrome with dementia and AD pathology (DS/AD), Pick's disease (PiD), progressive supranuclear palsy (PSP), Lewy body disease (LBD), Parkinson's disease (PD), corticobasal degeneration (CBD), and young and aged normal brains, and from two surgically resected gangliogliomas were immunostained using antibodies to Ki-67 (MIB-1 clone equivalent) and tau (tau). Ki-67 staining was performed following antigen retrieval by microwave heating. Ki-67 labeled NFT that were observed in the AD, DS/AD, PiD, PSP, LBD, and PD cases, one aged normal brain, and one ganglioglioma. Ki-67 generally labeled fewer NFT compared to tau. Pick bodies, ballooned neurons (Pick cells) in CBD and PiD, and nigral corticobasal inclusions in CBD were immunoreactive for tau but not Ki-67. Neither antibody labeled cortical or subcortical Lewy bodies. Our findings suggest that Ki-67 may be involved in the pathogenesis of neurofibrillary degeneration in AD, other neurodegenerative disorders, normal aging, and neoplasms such as ganglioglioma. We postulate a possible role for Ki-67 in the production of the abnormally phosphorylated tau protein that leads to the formation of paired helical filaments within susceptible neurons.

Role of the dorsomedial nucleus of the thalamus in Alzheimer's disease

It is not known whether changes in the thalamus play a role in the memory loss or dementia of Alzheimer's disease (AD), although trauma, infarction, and hemorrhage to the thalamus, particularly the dorsomedial nucleus (DMN), can cause these cognitive changes. To determine the pathologic changes in the DMN in AD, we examined the DMN in 16 cases of AD and 7 age-matched controls, with quantitative assessments of the total neuronal population and synaptic density, Alz-50-positive neurons, neurofibrillary tangles (NFT), and senile plaques (SP). We examined sections after staining with cresyl violet, a silver stain, and immunocytochemical staining for Alz-50 and synapsin I. Stereologic analysis demonstrated a mean loss of 29% of DMN neurons in AD and a synaptic density decrease of 21%. Alz-50 staining and NFT were present in all AD cases but in none of the controls. Senile plaques were 52 times more frequent in the DMN in AD than in the age-matched controls. The large variation in pathologic changes among our AD cases suggests that neuronal losses and other pathology in the DMN in AD may contribute to the total brain burden of pathology resulting in dementia in some AD patients, but not in others.

Apolipoprotein E genotype and Lewy body disease

To determine whether apolipoprotein E (APOE) genotype affects neuropathology in Lewy body disease (LBD), we examined 18 cases of LBD that did not have concurrent Alzheimer's disease by the CERAD criteria. We obtained APOE genotypes, determined diffuse beta-amyloid plaque (A beta P) and Lewy body densities in multiple brain regions, and graded the intensity of CA2-3 ubiquitin-positive neurites, vacuolar change, nigral pathology, amyloid angiopathy, and subpial amyloid deposition. The APOE allele frequencies were as follows: epsilon 2, 0.14 +/- 0.07; epsilon 3, 0.64 +/- 0.08; and epsilon 4, 0.22 +/- 0.03. The mean A beta P density was lower in APOE epsilon 3/3 cases (14.5 A beta Ps per mm2) than in the groups with the APOE epsilon 2 (67.0) or APOE epsilon 4 (46.6) alleles. This difference was due largely to the difference between A beta P density in the APOE epsilon 2 group and the APOE epsilon 3/3 group (F = 5.525, p < 0.02). CA2-3 neuritic degeneration was greater in those with the APOE epsilon 4 allele than in those with the APOE epsilon 3/3 genotype (grade = 1.9 +/- 1.3 versus 0.938 +/- 0.9; Kruskal-Wallis test statistic = 6.962, p < 0.05). These data are consistent with the hypothesis that APOE genotype may affect neuropathology in LBD.

Alzheimer's disease and Lewy body disease: a comparative clinicopathological study

The exact nature of the relationship between Lewy body disease and Alzheimer's disease (AD) is unknown. To investigate this, we compared cases of pure Lewy body disease, mixed Lewy body disease with AD, and pure AD to see what pathological features were shared and how they differed. We counted neurons, Lewy bodies, diffuse and neuritic senile plaques, neurofibrillary tangles, and neuropil threads in the frontal and medial temporal cortex and hippocampus from 5 autopsied cases of Lewy body disease (without AD histopathology), 7 with combined Lewy body disease and AD, 6 with AD, and 5 age-matched normal control subjects. Average neuronal counts in the cases with Lewy body disease were indistinguishable from those of control subjects, but higher than those for AD and combined Lewy body disease and AD. Diffuse plaque densities were similar in all disease forms. Neuritic senile plaques, neurofibrillary tangles, and neuropil threads were numerous in AD and combined Lewy body disease and AD, but sparse or absent in Lewy body disease and controls. Pure Lewy body disease and AD appear to be distinct clinicopathological entities except for the common feature of diffuse plaques in both disorders.

Vascular amyloid deposition in Alzheimer's disease. Neither necessary nor sufficient for the local formation of plaques or tangles

OBJECTIVE

To determine the relationship between vascular beta-amyloid (beta A4) and senile plaques (SPs) and neurofibrillary tangles (NFTs).

DESIGN

We counted vascular amyloid deposition with SP and NFT density in the medial temporal lobe (CA1 plus the subiculum) and the cerebellum.

PATIENTS

The brains of seven patients with Alzheimer's disease and of three age-matched nondemented control subjects were studied.

RESULTS

In Alzheimer's disease, the density of beta A4-laden blood vessels was significantly higher in the cerebellum than in CA1 plus the subiculum. Conversely, the densities of SPs and NFTs were much greater in the CA1 plus the subiculum than in the cerebellum.

CONCLUSIONS

This study indicates that local vascular beta A4 deposition is not directly correlated with SP and NFT densities. Deposition of beta A4 in blood vessel walls may not be instrumental in the formation of SPs and/or NFTs in the brain.

Cortical tubers demonstrate reduced immunoreactivity for synapsin I

To evaluate the effects of tuberous sclerosis (TS) on cortical synaptic organization, we analyzed synaptic densities within cortical tubers from the brains of two TS patients using a polyclonal antibody directed against synapsin I, a synaptic terminal-specific protein. The synaptic densities of the tubers and adjacent histologically normal cortex were obtained by determining optical densities using an IBAS (Zeiss) image analysis system. The tubers showed abnormally low levels of synapsin I compared with the normal cortex. The data suggest that cortical tubers do not contain a normal complement of synapses. This may reflect focal underdevelopment of normal cortical-cortical connections. Altered afferent cortical projections may also contribute to synaptic loss in cortical tubers.

The indusium griseum in Alzheimer's disease: an immunocytochemical study

The immunocytochemical features of the indusium griseum (IG) were compared with the corresponding hippocampus in 5 patients with Alzheimer's disease (AD) and 5 age-matched nondemented individuals using antibodies against beta-amyloid, the A68 protein (Alz-50 antibody), tau, ubiquitin and synapsin I. beta-Amyloid-positive plaques were prominent in the AD hippocampus but were not present in the IG. Numerous Alz-50, tau and ubiquitin-positive neurofibrillary tangles and dystrophic neurites were observed in the AD hippocampus but were infrequent in the IG. Synapsin I immunoreactivity was significantly reduced in both the AD hippocampus and the AD IG when compared to age-matched patients. These findings suggest that the IG may be resistant to factors that trigger production of abnormal AD-associated proteins. Loss of synaptic input alone may not account for the AD-associated changes in the hippocampus since synaptic depletion was seen in both the hippocampus and the unaffected AD IG.

Alzheimer's disease and aging: effects on perforant pathway perikarya and synapses

The hippocampal perforant pathway originates in the entorhinal cortex (ERC) and terminates in the outer molecular layer of the dentate gyrus (DG). To compare the effects of normal aging and Alzheimer's disease (AD) on the elements of the perforant pathway, we compared relative perikaryal numbers (determined by counting cell bodies and estimating volumes) in layer II of the ERC with synaptic quantities (estimated from immunoreactivity for the synaptic terminal protein synapsin I and DG volume) in the molecular layer of the DG. The brains of 5 young and 9 elderly cognitively normal individuals, and of 9 AD patients were studied. In normal aging we found a significant age-related decline in perikaryal numbers in the ERC without demonstrable synaptic loss in the DG. In AD there was marked and equivalent, (or proportional) reduction in both ERC perikaryal numbers and DG synapses. These data suggest that in normal aging remaining neurons may continue to support a full array of synapses, perhaps due to mechanisms such as axonal sprouting, synaptic enlargement, or synaptic ingrowth. In AD, however, the accelerated neuronal loss may overwhelm such compensatory mechanisms or alternatively, independent synaptic and perikaryal losses may occur.

Architecture of the suprachiasmatic nuclei in BALB/c and C57BL/6 inbred mouse strains

Quantitative values representing the length, girth, volume, shape, and cell counts of the suprachiasmatic nuclei (SCN) were measured in BALB/cByJ and C57BL/6J inbred mouse strains, which exhibit a large interstrain difference in the free-running period of their circadian locomotor rhythms. There were no differences in the gross architectural features of the SCN in these two strains.

Immunocytochemical study of ballooned neurons in cortical degeneration with neuronal achromasia

We studied the immunocytochemical characteristics of the ballooned neurons (BN) in three patients with cortical degeneration with neuronal achromasia (CDNA) using antibodies to phosphorylated neurofilaments (PNF), tau, Alz-50, ubiquitin, beta (A4) amyloid, and glial fibrillary acidic protein. All BN exhibited intense perikaryal staining for PNF protein. Most BN and some normal-appearing neurons also stained for ubiquitin and Alz-50. The BN did not immunostain for tau protein, and none of the cases had tau-reactive neocortical neurofibrillary tangles or Pick bodies. One case had occasional senile plaques that stained for beta amyloid; no case had amyloid angiopathy. Our findings suggest that the pathophysiologic basis of the cortical degeneration in CDNA involves an alteration of neuronal cytoskeletal metabolism affecting neurofilament and possibly microtubular proteins in conjunction with activation of the ubiquitin proteolytic system.

Primary progressive aphasia with focal neuronal achromasia

We describe the clinical, radiologic, neuropsychological, and neuropathologic features of a 69-year-old man with a 3-year history of progressive transcortical expressive aphasia. Neuropsychological testing showed progressive dysfunction of expressive language. Neuropathologic examination demonstrated focal cortical degeneration involving the left superior frontal gyrus, with swollen achromasic neurons and no evidence of Alzheimer's disease, Pick's disease, Creutzfeldt-Jakob disease, Lewybody disease, or other dementing disorders. This case adds to the known heterogeneity of the underlying pathology of patients with primary progressive aphasia.

Lobar atrophy with pontine neuronal chromatolysis ("ballooned" neurons)

A 64-year-old man developed progressive dementia over a period of 11 years. Postmortem examination showed severe atrophy of the temporal lobes of the brain with extensive neuronal loss and a remarkable alteration of the neuronal perikaryon--the "ballooned" neuron--restricted to the nuclei of the basis pontis. No neuritic plaques, neurofibrillary tangles, or Pick bodies were seen.

Corticonigral degeneration with neuronal achromasia. A clinicopathologic study of two cases

We describe the clinical and neuropathological features of two patients having corticonigral degeneration with neuronal achromasia (CND). Both patients had cognitive decline and movement disorders. Magnetic resonance (MR) scans showed cortical atrophy, which in one case was most prominent in the parasylvian region, and ventricular enlargement in both cases. Neuropathological examination revealed swollen achromasic neurons within the cerebral cortex and marked neuronal loss in the substantia nigra. No Pick bodies, Lewy bodies, histologic changes of Alzheimer's disease, or spongiform change were present in either case. The diagnosis of CND should be considered in patients with complex movement disorders, with or without abnormalities in cognitive function.

The indusium griseum: is it involved in Alzheimer's disease?

The histopathology of the indusium griseum (IG), a displaced hippocampal anlage, was studied in five patients with Alzheimer's disease (AD) and five controls. In the AD group, the IG had occasional neurons with granulovacuolar change (GVD) and rare Hirano bodies (HB), but no senile plaques (SP), neurofibrillary tangles (NFT), or neurons staining for phosphorylated neurofilament antigen. There was a slight but not statistically significant diminution of neurons within the IG. In all AD cases, the hippocampus showed abundant AD-associated histopathology. In the control cases, only rare neurons with GVD were present in the IG. These findings indicate that although single neurons within the IG may show some of the cytologic changes seen in the hippocampal neurons in normal aging and AD, IG neurons do not express the full range and severity of histopathologic abnormalities characteristic of AD. This suggests that factors other than selective vulnerability of neurons of hippocampal origin might be operating to induce the neuropathologic picture of AD.