Neuropathologic findings in cognitively normal older adults

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FOURTH INTERNATIONAL CONFERENCE ON ALZHEIMER’S DISEASE

PLENARY LECTURES III

448 GENETICS OF ALZHEIMER’S DISEASE. C. Van Broeckhoven. Neurogenetics Laboratory, Born Bunge Foundation, University of Antwerp (UIA), B-2610 Antwerpen, Belgium. Alzheimer disease (AD), the major form of senile dementia, is becoming a major health problem in developed countries. With aging populations the number of AD cases is increasing rapidly since no effective therapies are available because the primaly causes of AD have not yet been elucidated. Several researchers in different disciplines are actively contributing to the understanding of the AD pathology including molecular geneticists. A genetic etiology has been established for AD based on population survey, twin and family studies. Identification of the responsible genes may contribute to our understanding of the primary disease mechanisms and eventually lead to a more effective therapy. Initial genetic studies of AD using the positional cloning approach have identified 3 genetic loci for familial AD, 2 for presenile AD (mean onset age before 60 years) on chromosomes 21 and 14 respectively and 1 for senile AD (onset age after 60 years) on chromosome 19. The chromosome 21 locus coincided with the gene coding for PA4 amyloid, a major constituent of AD brain lesions and a proteolysis product of the amyloid precursor protein (APP). In total 6 different mutations were detected in the APP gene in familial AD patients and/or patients with cerebral amyloidosis. Together, these mutations account for no more than 5% of the familial presenile AD cases. Linkage studies have shown that approximately 70% of the presenile AD families have a genetic defect on chromosome 14 but the gene itself, located in 14q24.3, has not yet been identified. In general it seems that the chromosome 14 gene causes a disease onset before age 50 years, while AD patients with APP mutations have onset ages between 50 and 60 years. In senile AD families linkage and association studies have implicated a susceptibility locus on chromosome 19ql3. More recently, association studies have demonstrated that the e4 allele of the apolipoprotein E (apoE’4) gene located in 19q13.2, is a major risk factor for familial and sporadic AD, both senile and presenile AD. How apoE’4takes part in the AD pathology is currently being investigated

450 MOLECULAR BIOLOGY, GENETICS AND PROTEIN CHEMISTRY OF PRION DISEASES. M.A. Baldwin and S.B. Prusiner, University of California, San Francisco, CA 94143 USA. Enriching t?actions from Syrian hamster @Ha) brain for scrapie prion infectivity led to the discovery of the priori protein (RP). Priori diseases include scrapie of sheep. bovine spongiform encephalopatby of cattle, as well as Creutzfeldt-Jakob disease (CID) and GerstmannStrtiussler-Scheinker syndrome (GSS) of humans. Transgenic (Tg) mice expressing both SHa and mouse (MO)PrP genes were used to probe the molecular basis of the species barrier and the mechanism of scrapie priori replication. Bioassays of brain exuacts from two scrapie-infected Tg lines showed that the prior inoculum determines which prions are synthesized de MW, even though the cells express both PrP genes. Studies with artiBcial prions produced from chimeric MdSHaPrP uansgenes underscore the concept that inoculated priori dictates which prion will be replicated. Discovery of mutations in the RP genes of humans with GSS and familial CID established that prion diseases are both genetic and infectious. Tg mice expressing high (H) levels of MoPrP-PlOlL, corresponding to the GSS point mutation (P102L) in human PrP, spontaneously develop neurologic dysfunction, spongiform degeneration and astrocytic gliosis. Inoculation of brain extracts prepared from these Tg(MoPrP-PlOlL)H mice produced neumdegeneration in recipient animals after pmlonged incubation times. These results are in accord with those of other studies and argue that prions are devoid of foreign nucleic acid. Suuctutal investigations of PrPc and PrPSc suggest that the difference may be conformational. Spectroscopic analyses of secondary structure show that PrpC has a high a-helical content; whereas P@c has a g-sheet content higher than that predicted from the amino acid sequence. Conditions that diminished the B-sheet content of PrPk were the same as those identified previously that inactivate prion infectivity. Whether prion diversity as reflected by distinct “suains” producing different patterns of PrPk accumulation is due to different conformers of PrPk remains to be establsihed. Advances in the purification and characterization of both PrpC and PrPsc seem tc have identified the central event in PrPsc synthesis and priori propagation, i.e., the unfolding of a-helical domains followed by refolding into g-sheets. These fmdings underscore the fundamental features of priori structure and propagation that differentiate prions from other transmissible pathogens.

POSTER SESSION IV 449 THE PATHOLOGICAL LESIONS OF ALZHEIMER’S DISEASE; FORM AND FORMATION. D.M.A. Mann, Department of Pathological Sciences, University of Manchester, Manchester Ml3 9PT, Great Britain. It is now clear that not only do senile plaques (SP) and neurotibrillary tangles (NFT) constitute for diagnostic purposes the classical histopathological changes of Alzheimer’s disease (AD) but they also represent the critical sites of damage to the brain that result in neuronal dysfunction and clinical derangement. Many of the molecular characteristics of these lesions are now clear yet the mechanisms leading to their formation remain ill-defined as do their chronological and pathophysiological relationships. NFT contain, and may even be entirely composed of, abnormally phosphorylated tau proteins that are strongly associated with other molecules such as ubiquitin, heperan sulphate proteoglycan (HSPG), apolipoprotein E (ApoE) and amyloid P component. Plaques are complex sites of parenchymaldestructionbased on a focus of WA4 amyloid protein containing neural (dystrophic neurites) and gbal (microglia, astrocytes) elements. Complement proteins and pmtease inhibitors are associated with B/A4 as are ApoE and HSPG. The roles of these latter molecules in amyloid fibrillogenesis are not clear nor is it known what precise purpose the glial alterations subserve. A study of persons with Down’s syndrome provides a chronology to the disease process and implicates deposition of B/A4 as an initiating event. The similarly early appearance of ApoE within such deposits may facilitate this deposition. NFT appear later with regions such as entorhinal cortex and other temporal lobe structures being affected earlier than neucortical regions. Does this indicate early spread of disease or differential vulnerability? How, or indeed whether, g/A4 deposition, par se, might mediate NIT formation is not known, nor is it clear if other plaque components are necessary or critical in this respect.

Neuropathology 451 NEUROPATHOLOGIC FINDINGS IN COGNITIVELY NORMAL OLDER ADULTS. F.A. D.R. Wekstein2. D. Davis3. A. Beuscher and W.R Markesberyl3 Sanders-Brown Center on Aging, Alzheimer’s Disease Research Center, and the Departments of Neurology1 , Physiology2 and Pathology3, University of Kentucky Medical Center, Lexington, Kentucky 40536-0084 USA. Neuropathologic markers of Alzheime
Schmitt’,

The present data represent the findings from the first 12 autopsies of healthy older adults who have enrolled in a longitudinal study of mental functioning and brain donation. Annual mental status examinations are completed on over 300 volunteers and regional SP and NFT counts are completed postmortem to provide control data for comparison with AD patients. Twelve cognttively normal older adults were autopsied for the current study (mean aoe at autopsy = 77 9 years 8 men and 4 women). Plaque and NFT counts were obtalneo from rrontal. temporal. panetal. and OrXpltal cortrcal regrons and CA- I ana subiculum of the hippocampus. Four of these older aduns (3 men and 1 woman: mean autopsy age=785 range: 77 _ 02 years) met neuropathologic criteria for AD based on three or more regions with more than 15 SP 12.3 mm2 whereas the remaining eight (mean autopsy age=77.6, range: 69 - 98 years) were classined as normal. Analyses of the cognitive data showed no significant differences in years of education or on any of the cognitive measures as a result of neuropathologic classification even thouoh there were obvious differences in SP and NFT counts for all of the cortical region;. Correlations between SP and NFT counts, and the mental

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FOURTH INTERNATIONAL CONFERENCE ON ALZHEIMER’S DISEASE

Status examinations showed significant associations between age at autopsy and NFT counts (r = 0.67), Mini-Mental State Examination scores and hippocampal hippocampal NFT counts (I = -0.60), and a semantic memory/naming task and parietal SP counts (r = -0.64) as well as frontal NFT counts (r = -0.54). These preliminary data suggest that age-associated memory changes as reported whereas in the literature may be linked to accumulation of NFTs in hippocampus cognitive changes associated with preclinical AD may reflect a threshold of cortical neuropathology. Further, more sensitive measures of cognition that focus on semantic memory may provide a better index of early changes associated with the development of AD as documented by neuropathologic criteria. Supported in part by NIA grants PO1 AGO511Q and P50 lAG05144.

452 CORRElATlCNS BEIWEEN NEUROPSYCHOLCXXALAND NEUFtOPATHOLOGlCAL DATA IN ALZHEIMER’S DISEASE. P. Caramelli, Y. Robitaille, Y. Joanette, A.R. Lecours, A. Cholette and D. Gauvreau. Laboratoire ThBophile-Alajouanine and Projet IMAGE. Centre de recherche. Centre hospitalier C&e-des-Neiges, and Department of Pathology, University of Montreal, Montreal, Quebec, Anatomo-clinical correlative studies on Alzheimer’s disease (AD) that have been reported in the last few years have particularly searched for a relationship between neuropathological features and severity of dementia. This domain, however, still la&s qualitative research. A cohort of patients with AD has been followed in a population-based study (IMAGE Project) in the Province of Quebec (Canada), since 1989. by means of the PENO. a comprehensive protocol of neuropsychological evaluation meant to investigate most of the basic components of the cognitive profiles presented in aging and dementia. Five patients meeting NINCDS-ADRDA criteria for probable AD and followed longitudinally with the PEN0 have been submitted to a detailed neuropathological post-mortem study. The maximum interval between the last evaluation and death was 5 months. The subjects were three women and two men, aged between 72 and 86 years at death (mean-77.6). with duration of disease ranging from 2 to 6 years (mean=3.7). All subjects were between stages 4 and 5 on Reisberg’s Global Deterioration Scale. Neurological examination disclosed no motor or sensory abnormalities in any of the cases. Memory deficits were observed in all subjects. For language, praxis and gnosis, however, there was a striking heterogeneity. For example, one subject had marked visuo-spatial difficulties, whilst three others had a predominance of language impairment with additional visuo-spatial deficits in one. The last subject presented a severe constructional apraxia. Neuropathological examination confirmed AD in four cases. The fifth case showed senile plaques and neurofibrillary tangles which, however, were below the quantitative diagnostic threshold of AD. The topographical distribution of tangles revealed a good correlation with the neuropsychological profiles in at least two cases: one subject with predominant language deficits had the highest density of neurofibrillary tangles in the left inferior parietal cortex: in another case, presenting marked language and visuo-spatial disturbances, the density of tangles was maximal in the left parietal cortex and in the fusiform gyrus. Brain specimens have also been submitted to additional neuropathological studies, mostly at the molecular level. The relationships between neuropathological and neuropsychological data shall be further discussed. Systematic investigation of the correlations between structural and clinical data in AD - based on detailed neuropsychological aad neuropathological information - should offer new insights on the complex nature of the pathophysiolcgy of the neuropsychological manifestations of the disease.

Some of the higher scores in group I depended on vague, round, disturbances in the interneuronal network: this plaque type should perhaps be ignored in a rating system. The zero scores in group II show that many clinical problems cannot be solved by a classical neuropathological approach. The higher scores in group II and the lower scores in group III mainly depended on temporal lobe pathology in elderly controles and patients. The extremely high scores in group IV were mainly caused by many, large, congophilic plaques in all areas. The following main conclusions are drawn. Researchers who use Alzheimer tissue from Brain Banks should be aware of the variable content of Alzheimer lesions. Also, the severity of clinical disease may not be fully expressed in the classical Alzheimer changes. Moreover, Alzheimer’s disease may represent a spectrum and not be homogenous.

454 CLINICAL PATHOLOGICAL CORRELATIONS IN 290 CONSECUTIVE AUTOPSIESIN PATIENTSWITH DEMENTIA .P. Antuono, J. Jones, G. Dal Forno, K-C Ho, J. Beyer, , K. Nicholson, A. Bloom. The Medical College of Wisconsin, Depts. of Neurology and Pharmacology. VAMC, Milwaukee WI. 53226 USA. We reviewed 290 consecutive autopsies performed by the Alzheimer’s Disease Wisconsin Brain Bank during the period 1986-1994. Our objective was to determine the accuracy of the clinical-pathological diagnosis and the yield of tissue available for research in AD. Among the patients enrolled in the prospective autopsy program, 237 were clinically demented. The clinical diagnosis of Probable AD (NINCDYADRDA criteria) was made in 164 cases (58%) and possible AD in 14 other (8%). A second group of 22 (7%)was simply diagnosed during life as having dementia: the remainder (64% of total autopsies performed) included various diagnoses including 3 cases of JacobCreutzfeld disease (J-C). Of the 164 Probable AD cases, 90 (55%) were confirmed at autopsy, 25 cases (15%) had AD with multi-infarct dementia (MID), 21 cases (18%) AD with Parkinson’s disease (PD), 8 (5%) had a combination of AD, PD and MID. Of the remaining 15 cases, 13 (8%) had pathological findings consisting of simple neuronal loss and gliosis, 3 (2%) had MID, one Lewy body disease and one J-C. Among the 22 cases in the group diagnosed clinically as dementia, 7 cases (31%) had AD, 7 (31%) had AD and MID, 4 (18%) simple neuronal loss with gliosis and 4 (18%) with other diagnoses. The correlation between clinical diagnosis of probable AD and autopsy confirmation is 87%. Many co-morbidities (MID and PD) present with AD, were not identified clinically (39% of cases examined). The correlation between the clinical diagnosis of AD and “pure” cases of AD at autopsy would therefore be only 55%. These data suggest that in spite of a good diagnostic clinical pathological correlation, only a minority of cases were appropriate for research studies.

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453 NEUROPATHOLOGICAL SCORES OF ALZHEIMER CHANGES W. Kamphorst*, F.C. Starn*O, R. Ravid” and D.F. SwaabO * Free University Hospital, Dept. of Pathology, Amsterdam, the Netherlands o Netherlands Brain Bank, Amsterdam, the Netherlands Four patient groups were examined neuropathologically in a semiquantitative way. Group I (n=33) consisted of non-demented neurologically normal controls, group II (n=l6) consisted of cases with clinically probable Alzheimer’s disease that could not be neuropathologically confirmed, group III (n= 110) contained neuropathologically confirmed Alzheimer cases fitting the Khatchatuxian criteria, and group IV was composed of 6 demented Down patients. In 4 cortical areas (mediofrontobasal, temporal lobe, superior and inferior parietal lobules, occipital lobe) 5 features (congophilic senile plaques, congophilic anglopathy, argyrophilic (Bodian) senile plaques, neurofibrlllary tangles, disturbance of the intemeuronal network) were scored (O-3 points). Adding these scores resulted in a sum scOre for every case (maximum: 4x5~3 = 60). The sum scores were O-21 (median 3) for group I, O-28 (median 14) for group II, 13-56 (median 34) for group III, 52-60 (median 55) for group IV.

SIMILARITIES AND DISSIMILARITIES BETWEEN ALTERED NEURITES IN SENILE PLAQUES AND NEUROPIL THREADS IN AND BETWEEN AlZHEIMER AND NONAlZHEIMER’S DISEASE: DEMENTED ELD LY SENILE PLAQUES. Iv Psychiatry’, NeuOS.S.Zhanl R.Veerhuis ,W.Ka horstand’,P.Eikelenboonl.Cept.of 1p patholcqyil and Pharsacoloqy lledlcal Faculty, Free University, Amsterdam,The Nether-

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lands. We imnocytochesically studied the characteristics of altered neurites in frozen sections fron neocortexes of 10 Alzheimer disease IMI cases laqed 4049 years1 and 15 non-dementedcontrols (aqed 51-91 years). B/A4 imnostained plaques Iwere found in all M cases with high density. Of 15 controls 11 cases showed B/Al deposits in neocortex. In 5 out of the 11 B/Al positive controls, the density of plaques reached the same level as found in AD cases. However, the anyloid plaques in those 11 cases xere Mainly of the diffuse type. much less classical plagues with Conqo red cores lCPl could be seen in the controls comparing with M cases. In both AD and control cases, the altered neurites in the coronas of CP were often isnunostained by antibodies to N and C terminals of anyloid precursor protein lAPP), GAP43, collagenIV, laminin and the inteqrin receptor-VLA6. The altered neurites in CP coronas in AD, but not in controls, were also imnostained ;uith tau2 and ubiouitin antibodies. Imunolabelina for ohosohorvlated neurofilawntSHI34 was also see’n in CP coronas in AD, but only’occasionaily ;een in the controls. Immnolahelinq for HAP2was not found in CP fron both groups. Extensive neuropil threads INTI and many neurofibrillary tangles lNPTl imunostained by tau2 and ubiguitin antibodies were present in AD neocortex, but not seen in control cases. Soae NT and NFTcould be stained with C-terminal APP antibody. However! NT and NPT could not be imunostained by N-teninal of AFP, GAP43, CollaqenIV, laslnin and VLA6antibodies. Our findings indicate that in AD cases altered neurites in CP are undergoing both an aberrant sprouting process and a degenerating process. They are probably from axon