B. T. Hyman

Bio: B. T. Hyman is an academic researcher from Harvard University. The author has contributed to research in topics: Apolipoprotein E & Alzheimer's disease. The author has an hindex of 32, co-authored 60 publications receiving 4792 citations.

Early Aβ accumulation and progressive synaptic loss, gliosis, and tangle formation in AD brain

Abstract: Background: Pathologic changes in the Alzheimer disease (AD) brain occur in a hierarchical neuroanatomical pattern affecting cortical, subcortical, and limbic regions. Objective: To define the time course of pathologic and biochemical changes—amyloid deposition, amyloid β-peptide (Aβ) accumulation, neurofibrillary tangle (NFT) formation, synaptic loss, and gliosis—within the temporal association cortex of AD cases of varying disease duration, relative to control brains. Methods: Stereologic assessments of amyloid burden and tangle density as well as ELISA-based measurements of Aβ, synaptophysin, and glial fibrillary acidic protein (GFAP) were performed in the superior temporal sulcus from a cohort of 83 AD and 26 nondemented control brains. Results: Relative to control cases, AD brains were characterized by accumulation of NFT and amyloid plaques, increase of tris- and formic acid–extractable Aβ species, reduced levels of synaptophysin, and elevated levels of GFAP. In AD cases, the duration of dementia correlated with the degree of tangle formation, gliosis, and synaptic loss but not with any Aβ measures. Accumulation of Aβ, measured both neuropathologically and biochemically, was markedly increased in AD brains independent of disease duration, even in cases of short duration. Conclusions: These data support distinct processes in the initiation and progression of AD pathology within the temporal cortex: Deposition of Aβ reaches a “ceiling” early in the disease process, whereas NFT formation, synaptic loss, and gliosis continue throughout the course of the illness.

Association of apolipoprotein E epsilon2 and vasculopathy in cerebral amyloid angiopathy.

Abstract: Objective: Hemorrhage related to cerebral amyloid angiopathy (CAA) appears to occur through a multistep pathway that includes deposition of β-amyloid in cerebral vessels and specific vasculopathic changes in the amyloid-laden vessels, such as cracking of the vessel wall. Recent reports suggest a positive association between CAA-related hemorrhage and both the apolipoprotein E (APOE) ϵ4 allele and, unexpectedly, the APOE ϵ2 allele. Unlike APOE ϵ4, APOE ϵ2 does not appear to act through increased β-amyloid deposition. We therefore sought to determine whether it might specifically accelerate the second step in this pathway, that is, development of the vasculopathic changes that lead to hemorrhage. Methods: To determine the role of APOE in development of vasculopathic changes, we compared APOE genotypes in two groups of postmortem brains: 52 brains with complete amyloid replacement of vessel walls but without vasculopathic changes, and 23 brains with complete amyloid replacement of vessels with the accompanying changes of cracking of the vessel wall and paravascular leaking of blood. Results: Frequency of APOE ϵ2 was significantly greater in the group with vasculopathy (0.09) than the group without (0.01, p = 0.03). The groups did not differ in mean age or extent of neuritic plaques. Analysis of a clinical series of patients with CAA-related hemorrhage confirmed an overrepresentation of APOE ϵ2 as well as an association between this allele and earlier age of first hemorrhage. Conclusions: These data suggest that APOE ϵ2 and ϵ4 might promote CAA-related hemorrhage through separate mechanisms: ϵ4 by enhancing amyloid deposition and ϵ2 by causing amyloid-laden vessels to undergo the vasculopathic changes that lead to rupture.

Neurotoxic effects of thioflavin S-positive amyloid deposits in transgenic mice and Alzheimer's disease

Abstract: Despite extensive deposition of putatively neurotoxic amyloid-β (Aβ) protein in the brain, it has not been possible to demonstrate an association of Aβ deposits with neuronal loss in Alzheimer's disease (AD), and neuronal loss is minimal in transgenic mouse models of AD. Using triple immunostaining confocal microscopy and analyzing the images with the cross-correlation density map method from statistical physics, we directly compared Aβ deposition, Aβ morphology, and neuronal architecture. We found dramatic, focal neuronal toxicity associated primarily with thioflavin S-positive fibrillar Aβ deposits in both AD and PSAPP mice. These results, along with computer simulations, suggest that Aβ develops neurotoxic properties in vivo when it adopts a fibrillar β-pleated sheet conformation.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Hypothetical model of dynamic biomarkers of the Alzheimer's pathological cascade

Abstract: Summary Currently available evidence strongly supports the position that the initiating event in Alzheimer's disease (AD) is related to abnormal processing of β-amyloid (Aβ) peptide, ultimately leading to formation of Aβ plaques in the brain. This process occurs while individuals are still cognitively normal. Biomarkers of brain β-amyloidosis are reductions in CSF Aβ 42 and increased amyloid PET tracer retention. After a lag period, which varies from patient to patient, neuronal dysfunction and neurodegeneration become the dominant pathological processes. Biomarkers of neuronal injury and neurodegeneration are increased CSF tau and structural MRI measures of cerebral atrophy. Neurodegeneration is accompanied by synaptic dysfunction, which is indicated by decreased fluorodeoxyglucose uptake on PET. We propose a model that relates disease stage to AD biomarkers in which Aβ biomarkers become abnormal first, before neurodegenerative biomarkers and cognitive symptoms, and neurodegenerative biomarkers become abnormal later, and correlate with clinical symptom severity.

Effects of Age, Sex, and Ethnicity on the Association Between Apolipoprotein E Genotype and Alzheimer Disease: A Meta-analysis

Abstract: Objective. —To examine more closely the association between apolipoprotein E (APOE) genotype and Alzheimer disease (AD) by age and sex in populations of various ethnic and racial denominations. Data Sources. —Forty research teams contributed data onAPOEgenotype, sex, age at disease onset, and ethnic background for 5930 patients who met criteria for probable or definite AD and 8607 controls without dementia who were recruited from clinical, community, and brain bank sources. Main Outcome Measures. —Odds ratios (ORs) and 95% confidence intervals (Cls) for AD, adjusted for age and study and stratified by major ethnic group (Caucasian, African American, Hispanic, and Japanese) and source, were computed forAPOEgenotypes ∈2/∈2,∈2/∈3,∈2/∈4,∈3/∈4 and ∈4/∈4 relative to the ∈3/∈3 group. The influence of age and sex on the OR for each genotype was assessed using logistic regression procedures. Results. —Among Caucasian subjects from clinic- or autopsy-based studies, the risk of AD was significantly increased for people with genotypes ∈2/∈4 (OR=2.6, 95% Cl=1.6-4.0), ∈3/∈4 (OR=3.2, 95% Cl=2.8-3.8), and ∈4/∈4 (OR=14.9, 95% CI=10.8-20.6); whereas, the ORs were decreased for people with genotypes ∈2/∈2 (OR=0.6, 95% Cl=0.2-2.0) and ∈2/∈3 (OR=0.6, 95% Cl=0.5-0.8). TheAPOE∈4-AD association was weaker among African Americans and Hispanics, but there was significant heterogeneity in ORs among studies of African Americans (P Conclusions. —TheAPOE∈4 allele represents a major risk factor for AD in all ethnic groups studied, across all ages between 40 and 90 years, and in both men and women. The association betweenAPOE∈4 and AD in African Americans requires clarification, and the attenuated effect ofAPOE∈4 in Hispanics should be investigated further.

Tracking pathophysiological processes in Alzheimer's disease: an updated hypothetical model of dynamic biomarkers.

Abstract: Summary In 2010, we put forward a hypothetical model of the major biomarkers of Alzheimer's disease (AD). The model was received with interest because we described the temporal evolution of AD biomarkers in relation to each other and to the onset and progression of clinical symptoms. Since then, evidence has accumulated that supports the major assumptions of this model. Evidence has also appeared that challenges some of our assumptions, which has allowed us to modify our original model. Refinements to our model include indexing of individuals by time rather than clinical symptom severity; incorporation of interindividual variability in cognitive impairment associated with progression of AD pathophysiology; modifications of the specific temporal ordering of some biomarkers; and recognition that the two major proteinopathies underlying AD biomarker changes, amyloid β (Aβ) and tau, might be initiated independently in sporadic AD, in which we hypothesise that an incident Aβ pathophysiology can accelerate antecedent limbic and brainstem tauopathy.