Twin pairs discordant for neuropathologically confirmed Lewy body dementia.

AIM: Little is known about the concordance rate in twins for dementia with Lewy bodies (DLB). The rate of agreement between clinical and pathological diagnoses for DLB is typically low, necessitating confirmation of the diagnosis neuropathologically. METHODS: Participants were 17 twin pairs enrolled in the Duke Twins Study of Memory in Aging in which at least one member of the pair had an autopsy confirmed diagnosis of DLB, Alzheimer's disease (AD) with Lewy bodies or frontotemporal dementia with Lewy bodies. The characteristics of those with dementia were assessed and rates of concordance for pathological confirmed dementia were examined. RESULTS: Four monozygotic twin pairs had a proband with neuropathologically confirmed pure DLB; all remained discordant for dementia for periods up to 16 years or more. Five of 13 pairs in which the proband had AD plus DLB were concordant for dementia but only one pair was concordant for AD plus DLB, while the co-twins in the other four pairs had other types of dementia. CONCLUSIONS: The present study indicates that even among twins, a diagnosis of DLB in one twin does not predict the same diagnosis in the other twin. Neuropathological discordance in type of dementia among monozygotic pairs hints at environmental or epigenetic factors playing a role in Lewy body pathology.

Longitudinal follow-up of late-onset Alzheimer disease families.

Historically, data for genetic studies are collected at one time point. However, for diseases with late onset or with complex phenotypes, such as Alzheimer disease (AD), restricting diagnosis to a single ascertainment contact may not be sufficient. Affection status may change over time and some initial diagnoses may be inconclusive. Follow-up provides the opportunity to resolve these complications. However, to date, previous studies have not formally demonstrated that longitudinally re-contacting families is practical or productive. To update data initially collected for linkage analysis of late-onset Alzheimer disease (LOAD), we successfully re-contacted 63 of 81 (78%) multiplex families (two to 17 years after ascertainment). Clinical status changed for 73 of the 230 (32%) non-affected participants. Additionally, expanded family history identified 20 additional affected individuals to supplement the data set. Furthermore, fostering ongoing relationships with participating families helped recruit 101 affected participants into an autopsy and tissue donation program. Despite similar presentations, discordance between clinical diagnosis and neuropathologic diagnosis was observed in 28% of those with tissue diagnoses. Most of the families were successfully re-contacted, and significant refinement and supplementation of the data was achieved. We concluded that serial contact with longitudinal evaluation of families has significant implications for genetic analyses.

Microvascular injury and blood-brain barrier leakage in Alzheimer's disease.

Thinning and discontinuities within the vascular basement membrane (VBM) are associated with leakage of the plasma protein prothrombin across the blood-brain barrier (BBB) in Alzheimer's disease (AD). Prothrombin immunohistochemistry and ELISA assays were performed on prefrontal cortex. In severe AD, prothrombin was localized within the wall and neuropil surrounding microvessels. Factor VIII staining in severe AD patients indicated that prothrombin leakage was associated with shrinkage of endothelial cells. ELISA revealed elevated prothrombin levels in prefrontal cortex AD cases that increased with the Braak stage (Control=1.39, I-II=1.76, III-IV=2.28, and V-VI=3.11 ng prothrombin/mg total protein). Comparing these four groups, there was a significant difference between control and Braak V-VI (p=0.0095) and also between Braak stages I-II and V-VI (p=0.0048). There was no significant difference in mean prothrombin levels when cases with versus without cerebral amyloid angiopathy (CAA) were compared (p-value=0.3627). When comparing AD patients by APOE genotype (ApoE3,3=2.00, ApoE3,4=2.49, and ApoE4,4=2.96 ng prothrombin/mg total protein) an analysis of variance indicated a difference between genotypes at the 10% significance level (p=0.0705). Tukey's test indicated a difference between the 3,3 and 4,4 groups (p=0.0607). These studies provide evidence that in advanced AD (Braak stage V-VI), plasma proteins like prothrombin can be found within the microvessel wall and surrounding neuropil, and that leakage of the blood-brain barrier may be more common in patients with at least one APOE4 allele.

Recovery and expression of messenger RNA from postmortem human brain tissue.

The Bryan Alzheimer's Disease Research Center Rapid Autopsy Program at Duke University Medical Center obtains postmortem human brain tissue for experimental investigations. We evaluated 19 brains for RNA integrity and mRNA gene expression. Nine were from patients diagnosed with Alzheimer's disease, and ten were from nondemented controls. In all cases, the following variables were recorded: postmortem procurement delay (range, 1 hour and 10 minutes to 14 hours), pH of cerebrospinal fluid, premortem fever or sepsis, provision of supplemental oxygen in the agonal period, and temporal relation to time of death (either sudden death or protracted illness). Total RNA was extracted, quantified, and evaluated by agarose gel electrophoresis and quantitative gene expression analysis of 18S rRNA and edg-1 using TaqMan technology. All samples appeared to yield intact RNA without significant degradation, and expression of the edg-1 gene was detected by the real time reverse transcriptase polymerase chain reaction in all cases. We conclude that intact RNA can be obtained from postmortem human brain tissue, even in patients with severe premortem illnesses and delayed postmortem tissue procurement intervals. However, we caution that the successful expression of certain genes from postmortem brain tissue may require enhanced procurement efforts to maximize RNA integrity.

Ham56-immunoreactive macrophages in untreated infiltrating gliomas.

CONTEXT: Classic diagnostic neuropathologic teachings have cautioned against making the diagnosis of neoplasia in the presence of a macrophage population. The knowledge of macrophage distribution should prove useful when confronted with an infiltrating glioma containing macrophages. OBJECTIVE: To identify macrophages in untreated, infiltrating gliomas using the monoclonal antibody HAM56, and to confirm their presence in an untreated glioblastoma multiforme (GBM) with the serial analysis of gene expression (SAGE) method. METHODS: We evaluated the presence of macrophages in 16 cases of untreated, supratentorial infiltrating gliomas with the macrophage monoclonal antibody HAM56. We performed SAGE for one case of GBM and for normal brain tissue. RESULTS: In World Health Organization (WHO) grade II well-differentiated astrocytoma and oligodendroglioma, HAM56 reactivity was noted only in endothelial cells, and unequivocal macrophages were not identified. In WHO grade III anaplastic astrocytoma and anaplastic oligodendroglioma, rare HAM56-positive macrophages were noted in solid areas of tumor. In WHO grade IV GBM, HAM56-positive macrophages were identified in areas of solid tumor (mean labeling index, 8.6%). In all cases of GBM, nonquantitated HAM56-positive macrophages were identified in foci of pseudopalisading cells abutting necrosis and in foci of microvascular proliferations. In none of the cases were granulomas or microglial nodules found, and there was no prior history of surgical intervention, radiation therapy, chemotherapy, or head trauma in these cases. By SAGE, the macrophage-related proteins osteopontin and macrophage-capping protein were overexpressed 12-fold and eightfold, respectively, in one untreated GBM compared with normal brain tissue. In this case, numerous HAM56-positive macrophages (labeling index, 24.5%) were present in the solid portion of tumor, and abundant nonquantified macrophages were identified in foci of pseudopalisading cells abutting necrosis and in foci of microvascular proliferations. CONCLUSIONS: This study confirms the utility of the monoclonal antibody HAM56 in identifying macrophages within untreated infiltrating gliomas. The overexpression of macrophage-related proteins in one case of GBM as detected by SAGE signifies that macrophages may be present in untreated GBMs.

Dementia with Lewy bodies and Alzheimer's disease.

To investigate similarities and differences between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), we undertook a demographic analysis of 277 patients from the Kathleen Price Bryan Brain Bank with an antemortem diagnosis of probable AD. Patients with additional, possibly confounding clinical and pathologic diagnoses such as infarcts, hematomas, neoplasms, and other neurodegenerative disorders, were excluded from the analysis. Neuropathologically, AD alone was present in 192 subjects (69%), and DLB was found in 85 subjects (31%). All of the DLB cases had neuropathologic evidence of AD sufficient to meet CERAD criteria for a diagnosis of definite AD plus nigral Lewy bodies. Gender, apolipoprotein E (APOE) genotype, brain weight, age at death, duration of disease and Braak stage were compared between the two groups. Statistical analyses were performed using Fisher's exact test for comparisons of categorical data and Student's t-test for comparison of means for continuous outcomes. The proportion of males and females was balanced in the combined AD and DLB populations. There was a highly statistically significant increased frequency of APOE 3/4 in males with DLB (P = 0.007). We found higher brain weights in males with DLB versus males with AD (P = 0.012). AD was more frequent in females and DLB was more frequent in males (P = 0.019). Our findings with respect to age at death, duration of disease and Braak stage within diagnostic groups confirm previously reported findings. These data suggest that Lewy bodies are more common in males affected with dementia, especially those with the APOE 3/4 genotype.

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

Lewy body and Alzheimer pathology in a family with the amyloid-beta precursor protein APP717 gene mutation.

Mutations in the amyloid precursor protein (APP) gene cause one form of early onset familial Alzheimer's disease (AD). One such family has been studied genetically and neuropathologically and represents the basis of the present report. Four siblings with the APP717 Val to Ile mutation, aged 59, 65, 61 and 64 years, apolipoprotein E (APOE) genotyped 2,4 (first three) and 2,3 respectively, had severe AD, Braak stage VI with frequent neurofibrillary tangles in the primary visual cortex, Brodmann area 17. The first one also met McKeith criteria for the limbic stage of dementia with Lewy bodies but did not have substantia nigra Lewy bodies. The second two met McKeith criteria for the neocortical stage of dementia with Lewy bodies and both had substantia nigra Lewy bodies. The fourth had AD but no Lewy bodies. A cousin without the APP717 mutation who was APOE 3, 4, developed dementia at age 60 and died at age 75. She had severe cerebrovascular atherosclerosis, less severe AD, Braak stage V, with sparing of area 17. She also had Lewy bodies in the substantia nigra and in the cortex and met McKeith criteria for neocortical stage of dementia with Lewy bodies. Extrapyramidal features were present in all five. Lewy bodies have been described in 53% of reported autopsies on individuals with the APP717 Val to Ile mutation coincident with dementia and AD neuropathologic changes. These observations suggest an association between the chromosome 21 APP mutation and Lewy body formation, possibly mediated by other environmental or genetic factors.

Ubiquitin immunochemistry as a diagnostic aid for community pathologists evaluating patients who have dementia.

Alzheimer's disease is the most common cause of dementia It is associated with genetic risk factors and at least three autosomal dominant mutations. Community pathologists are frequently asked by families to evaluate autopsy material for Alzheimer's disease. Neuropathologic diagnosis is based on technically difficult silver impregnation stains that may not be readily available to community-based pathologists. Because immunohistochemical techniques are more widely accessible, we evaluated the practical utility of using a single immunohistochemical stain for diagnosing Alzheimer's disease. The ubiquitin antigen was selected because of its presence in morphologically distinct deposits characteristic of several neurodegenerative diseases. Paraffin blocks were obtained from the Bryan Alzheimer's Disease Research Center Brain Bank, a repository of approximately 900 brains. Tissues from 16 individuals who exhibited the entire range of Alzheimer's-type neuropathology were selected. Ubiquitin immunostains, evaluated blindly and independently by four pathologists ranging from first-year resident trainee to experienced neuropathologist, reliably stained both neuritic plaques and neurofibrillary tangles essential for diagnosing and staging Alzheimer's disease. Nondemented controls with early Alzheimer's-type changes were easily distinguished from cases of definitive Alzheimer's disease. The stains also highlighted characteristic inclusions of Parkinson's disease or Lewy body dementia Ubiquitin immunohistochemistry is a reliable, reproducible, and readily available diagnostic aid for distinguishing Alzheimer's disease from other causes of dementia.

Fine mapping of the chromosome 12 late-onset Alzheimer disease locus: potential genetic and phenotypic heterogeneity.

Apolipoprotein E (APOE) is the only confirmed susceptibility gene for late-onset Alzheimer disease (AD). In a recent genomic screen of 54 families with late-onset AD, we detected significant evidence for a second late-onset AD locus located on chromosome 12 between D12S373 and D12S390. Linkage to this region was strongest in 27 large families with at least one affected individual without an APOE-4 allele, suggesting that APOE and the chromosome 12 locus might have independent effects. We have since genotyped several additional markers across the region, to refine the linkage results. In analyzing these additional data, we have addressed the issue of heterogeneity in the data set by weighting results by clinical and neuropathologic features, sibship size, and APOE genotype. When considering all possible affected sib pairs (ASPs) per nuclear family, we obtained a peak maximum LOD score between D12S1057 and D12S1042. The magnitude and location of the maximum LOD score changed when different weighting schemes were used to control for the number of ASPs contributed by each nuclear family. Using the affected-relative-pair method implemented in GENEHUNTER-PLUS, we obtained a maximum LOD score between D12S398 and D12S1632, 25 cM from the original maximum LOD score. These results indicate that family size influences the location estimate for the chromosome 12 AD gene. The results of conditional linkage analysis by use of GENEHUNTER-PLUS indicated that evidence for linkage to chromosome 12 was stronger in families with affected individuals lacking an APOE-4 allele; much of this evidence came from families with affected individuals with neuropathologic diagnosis of dementia with Lewy bodies (DLB). Taken together, these results indicate that the chromosome 12 locus acts independently of APOE to increase the risk of late-onset familial AD and that it may be associated with the DLB variant of AD.

Electron microscopic diagnosis of human flavivirus encephalitis: use of confocal microscopy as an aid.

The distinction between intracranial viral infections and inflammatory conditions requiring immunosuppression is important. Although specific laboratory reagents are readily available for some viruses, diagnosis of arbovirus infection is more difficult. Transmission electron microscopy (TEM) theoretically allows identification of viral particles independent of reagent availability, but it has limited sensitivity. We report two cases of human flavivirus encephalitis diagnosed by TEM. Laser scanning confocal microscopy (LSCM) was used in one case to survey unembedded tissue slices for focal abnormalities, from which fragments smaller than 1 mm2 were excised for epoxy embedding. This facilitated TEM identification of intracytoplasmic, budding, 35-40 nm spherical virus particles, confirmed by serology as St. Louis encephalitis. In contrast to mosquitoes and newborn mice, in which high viral loads are associated with minimal tissue responses, these biopsies showed florid angiodestructive inflammation and microgliosis, with rare virions in necrotic perivascular cells and astrocytes. To our knowledge, this represents the first ultrastructural study of St. Louis encephalitis in humans, indicating the potential value of LSCM-aided TEM.

Neuropathological features of frontotemporal dementia and parkinsonism linked to chromosome 17q21-22 (FTDP-17): Duke Family 1684.

Frontotemporal dementia with parkinsonism (FTDP-17) is an autosomal dominant disorder that presents clinically with dementia, extrapyramidal signs, and behavioral disturbances in mid-life and progresses to death within 5 to 10 years. Pathologically, the disorder is characterized by variable neuronal loss and gliosis in the frontal and temporal lobes, limbic structures, and the midbrain. Autopsied individuals from some kindreds display abundant neurofibrillary change while others, including a single affected individual from Duke Family 1684, lack distinctive histological features and exhibit only mild neuronal loss and gliosis in limbic structures and subcortical nuclei when examined by routine silver stain. Recently, mutations in the microtubule associated protein tau have been shown to segregate with the disease in this family and in many other affected kindreds. In order to examine the distribution of tau deposits, we performed tau immunohistochemistry, immunoblotting, and immunoelectron microscopy of tau-containing filaments. Immunohistochemistry revealed numerous tau deposits within glial cells and within neurons. Twisted ribbon-like filaments observed by immunoelectron microscopy were immunodecorated with tau AT8 antibody. Sarkosyl-insoluble tau extracted from the hippocampus and cortex migrated as 2 major bands at 64 and 68 kilodaltons and a minor band at 72 kilodaltons, which after alkaline phosphatase treatment appeared to contain mainly tau isoforms with 4 repeats. Furthermore, the ratio of soluble tau with 4 to 3 microtubule-binding repeats was increased. The role of tau mutations in this disorder is discussed in this paper.

Gliomatosis cerebri: cytologic and autopsy findings in a case involving the entire neuraxis.

We describe the case of a 7-year-old girl who was clinically diagnosed as having a pontine glioma based on magnetic resonance imaging studies. Neoplastic cells were identified upon cytologic examination of cerebrospinal fluid. Autopsy studies revealed an anaplastic astrocytoma (WHO grade III) diffusely infiltrating the cerebral hemispheres, brain stem, cerebellum, leptomeninges, and spinal cord to the level of the conus medullaris. The Ki-67 labeling index focally approached 30%. Although many of the neoplastic cells displayed elongated twisted nuclei reminiscent of microglia, these cells stained intensely for glial fibrillary acidic protein, supporting an astrocytic origin. Unusual features of this case of gliomatosis cerebri include involvement of the entire central neuraxis, correlation with pre-mortem lumbar puncture cytology, and a markedly elevated Ki-67 labeling index.

Paraneoplastic limbic encephalitis associated with small cell carcinoma of the prostate.

A 76-year-old man with primary small cell carcinoma of the prostate died after a subacute illness marked by memory loss and truncal ataxia Post-mortem examination of the central nervous system was consistent with limbic encephalitis and cerebellar degeneration. Although limbic encephalitis is a known complication of small cell carcinoma of the lung, this seems to be the first reported case of limbic encephalitis associated with small cell carcinoma of the prostate. Implications with respect to diagnosis and therapy are discussed.

December 1998--16 year old female with headaches, lethargy and a sellar/suprasellar mass.

A 16 year female with a history of developmental delay and shunted hydrocephalus presented with two months of progressive headaches, lethargy and visual disturbances. An MRI of the brain revealed a sellar and suprasellar cystic mass which was absent on a previous MRI six years earlier. The pre-operative clinical diagnosis was pituitary adenoma vs. craniopharyngioma. Histologically, the fibrous wall of the ciliated epithelial-lined cyst was thickened by non-caseating granulomatous inflammation, hemorrhage, hemosiderin, and cholesterol clefts, consistent with cyst rupture. Rathke's cleft cysts are uncommon symptomatic lesions in young people, and must be distinguished from craniopharyngioma.

Correlation of hippocampal neuronal density and FDG-PET in mesial temporal lobe epilepsy.

PURPOSE: Interictal [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60-80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE. METHODS: Forty-three patients with MTLE after anterior temporal lobectomy were included. Pathology demonstrated mesial temporal sclerosis (n = 41) or endfolium sclerosis (n = 2). Interictal FDG-PET scans were graded by visual analysis on a scale ranging from normal (grade 1) to severe (grade 5) hypometabolism. Neuronal counting was performed in the subiculum, hippocampal subfields, and dentate granular cell layer (DG). Neuronal density of patients was compared with that of seven autopsy controls. Data were compared by using Student's t tests and Kruskal-Wallis one-way analysis of variance (ANOVA). RESULTS: Significant neuronal loss in CA1 through CA4 and DG was found in patients compared with controls. Neuronal density in the subiculum, CA1, CA4, and DG did not correlate with severity of hypometabolism. However, patients with abnormal FDG-PET had higher neuronal density in CA2 and CA3 versus patients with normal studies. CONCLUSIONS: This study supports a previous observation that degree of FDG-PET hypometabolism does not parallel severity of hippocampal neuronal loss in MTLE.

Neuropathological and neuropsychological changes in "normal" aging: evidence for preclinical Alzheimer disease in cognitively normal individuals.

The presence of diffuse or primitive senile plaques in the neocortex of cognitively normal elderly at autopsy has been presumed to represent normal aging. Alternatively, these patients may have developed dementia and clinical Alzheimer disease (AD) if they had survived. In this setting, these patients could be subjects for cognitive or pharmacologic intervention to delay disease onset. We have thus followed a cohort of cognitively normal elderly subjects with a Clinical Dementia Rating (CDR) of 0 at autopsy. Thirty-one brains were examined at postmortem according to Consortium to Establish a Registry for Alzheimer Disease (CERAD) criteria and staged according to Braak. Ten patients were pathologically normal according to CERAD criteria (1a). Two of these patients were Braak Stage II. Seven very elderly subjects exhibited a few primitive neuritic plaques in the cortex and thus represented CERAD 1b. These individuals ranged in age from 85 to 105 years and were thus older than the CERAD la group that ranged in age from 72 to 93. Fourteen patients displayed Possible AD according to CERAD with ages ranging from 66 to 95. Three of these were Braak Stage I, 4 were Braak Stage II, and 7 were Braak Stage III. The Apolipoprotein E4 allele was over-represented in this possible AD group. Neuropsychological data were available on 12 individuals. In these 12 individuals, Possible AD at autopsy could be predicted by cognitive deficits in 1 or more areas including savings scores on memory testing and overall performance on some measures of frontal executive function.

Diagnosis of intracranial vasculitis: a multi-disciplinary approach.

Intracranial vasculitis, or primary angiitis of the central nervous system (PACNS), is an uncommon, often fatal disorder that frequently responds to aggressive immunosuppressive therapy. Magnetic resonance imaging (MRI), cerebral angiography, and brain biopsy are diagnostic modalities that vary in invasiveness and diagnostic accuracy. The purpose of this study was to determine whether certain clinical or radiologic features were predictive of a diagnostic biopsy. Thirty consecutive patients undergoing brain biopsy to "rule out vasculitis" were studied. Nine patients demonstrated granulomatous or lymphocytic vasculitis, 1 had lymphocytic vasculitis and encephalitis secondary to arbovirus infection, 5 had thickened vessels consistent with hypertensive changes, 5 had amyloid angiopathy and/or changes of Alzheimer disease, 5 demonstrated no pathologic abnormalities, and 1 each had acute infarct, vascular malformation, aneurysm, acellular fibrinoid necrosis, and demyelination. The spectrum of MRI and angiographic changes associated with PACNS were nonspecific, overlapping extensively with changes of chronic hypertension and amyloid deposition. The predictive values of brain biopsy (90-100%) were significantly higher than those of angiography (37-50%) or MRI (43-72%). In this study, morbidity associated with aggressive immunosuppression was significantly greater than that associated with cerebral angiography or brain biopsy. Thus, wedge biopsy of cortical and leptomeningeal tissues is central to the multi-disciplinary approach to a patient with clinical suspicion of PACNS.

Rapid brain autopsy. The Joseph and Kathleen Bryan Alzheimer's Disease Research Center experience.

OBJECTIVE: To develop a system for retrieving brain tissue within 1 hour after death in an effective and useful manner. DESIGN: Nurse clinicians were employed as study co-ordinators and were available to families 24 hours each day. SETTING: Autopsies were performed at Duke University Medical Center, Durham, NC, from 1985 through 1995. PARTICIPANTS: Neuropathology faculty, fellows, and residents, autopsy technicians; and brain bank staff. RESULTS: Fifty-one rapid autopsies with a postmortem interval of less than 1 hour have been performed. Four of these were normal controls, three were disease controls, and 44 represented Alzheimer's disease patients. Tissue retrieved at rapid autopsy has been distributed to 93 research teams, 30 of these located at Duke University Medical Center. Many researchers have received multiple shipments of tissue. CONCLUSIONS: The Bryan Alzheimer's Disease Research Center Rapid Autopsy Program at Duke University Medical Center has been successful in retrieving tissue from individuals with dementia and also from controls within 1 hour of death. The critical features of the success of this program have been the use of nurse clinicians who work closely with patients and their families to ensure a successful autopsy at the time of death and the maintenance of a 24-hour call schedule for nurses and neuropathology staff. Similar programs can be implemented for experimental work into the pathogenesis of a wide variety of human diseases in which the examination of human tissue is required.