Renata E.L. Ferretti

Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled‐up primate brain

The human brain is often considered to be the most cognitively capable among mammalian brains and to be much larger than expected for a mammal of our body size. Although the number of neurons is generally assumed to be a determinant of computational power, and despite the widespread quotes that the human brain contains 100 billion neurons and ten times more glial cells, the absolute number of neurons and glial cells in the human brain remains unknown. Here we determine these numbers by using the isotropic fractionator and compare them with the expected values for a human‐sized primate. We find that the adult male human brain contains on average 86.1 ± 8.1 billion NeuN‐positive cells (“neurons”) and 84.6 ± 9.8 billion NeuN‐negative (“nonneuronal”) cells. With only 19% of all neurons located in the cerebral cortex, greater cortical size (representing 82% of total brain mass) in humans compared with other primates does not reflect an increased relative number of cortical neurons. The ratios between glial cells and neurons in the human brain structures are similar to those found in other primates, and their numbers of cells match those expected for a primate of human proportions. These findings challenge the common view that humans stand out from other primates in their brain composition and indicate that, with regard to numbers of neuronal and nonneuronal cells, the human brain is an isometrically scaled‐up primate brain. J. Comp. Neurol. 513:532–541, 2009.

The dorsal raphe nucleus shows phospho-tau neurofibrillary changes before the transentorhinal region in Alzheimer's disease. A precocious onset?

Aims: Alzheimers disease (AD) is a progressive and irreversible disease. There is strong evidence that the progression of the phospho‐tau neurofibrillary cytoskeletal changes, rather than the β‐amyloid burden, is crucial in determining the severity of the dementia in AD. The Braak and Braak staging system (BB) focuses mainly on the cortical cytoskeletal pathology and classifies this progressive pathology into six stages, spreading from the transentorhinal region to primary cortices. Although it is reported elsewhere that the midbrains dorsal raphe nucleus (DR), which is connected with those areas of the cerebral cortex undergoing early changes during BB I and II, exhibits AD‐related cytoskeletal pathology, this nucleus has not been considered by the BB. Methods: To determine during which BB stage and how frequently the DR is affected by AD‐related neurofibrillary changes, we studied the DR of 118 well‐characterized individuals of the Brain Bank of the Brazilian Aging Brain Study Group categorized according to the BB. Thirty‐eight of these individuals were staged as BB = 0, and 80 as BB ≥ 1. Results: In all of the BB ≥ 1 individuals (cortical neurofibrillary changes were present at least in the transentorhinal region) and in more than 1/5 of the BB = 0 individuals neurofibrillary changes were detected in the supratrochlear subnucleus of the DR. Conclusions: These observations: (i) support the hypothesis of transneuronal spread of neurofibrillary changes from the DR to its interconnected cortical brain areas; and (ii) indicate that the supratrochlear subnucleus of the DR is affected by neurofibrillary changes before the transentorhinal cortex during the disease process underlying AD.

Brain bank of the Brazilian aging brain study group—a milestone reached and more than 1,600 collected brains

IntroductionBrain banking remains a necessity for the study of aging brain processes and related neurodegenerative diseases. In the present paper, we report the methods applied at and the first results of the Brain Bank of the Brazilian Aging Brain Study Group (BBBABSG) which has two main aims: (1) To collect a large number of brains of elderly comprising non-demented subjects and a large spectrum of pathologies related to aging brain processes, (2) To provide quality material to a multidisciplinar research network unraveling multiple aspects of aging brain processes and related neurodegenerative diseases.MethodsThe subjects are selected from the Sao Paulo Autopsy Service. Brain parts are frozen and fixated. CSF, carotids, kidney, heart and blood are also collected and DNA is extracted. The neuropathological examinations are carried out based on accepted criteria, using immunohistochemistry. Functional status are assessed through a collateral source based on a clinical protocol. Protocols are approved by the local ethics committee and a written informed consent form is obtained.ResultsDuring the first 21 months, 1,602 samples were collected and were classified by Clinical Dementia Rating as CDR0: 65.7%; CDR0.5:12.6%, CDR1:8.2%, CDR2:5.4%, and CDR3:8.1%. On average, the cost for the processing each case stood at US

Very low levels of education and cognitive reserve A clinicopathologic study

400. To date, 14 laboratories have been benefited by the BBBABSG.ConclusionThe high percentage of non-demented subjects and the ethnic diversity of this series may be significantly contributive toward aging brain processes and related neurodegenerative diseases understanding since BBBABSG outcomes may provide investigators the answers to some additional questions.

Repair of oxidative DNA damage, cell-cycle regulation and neuronal death may influence the clinical manifestation of Alzheimer's disease.

Objective: We conducted a clinicopathologic study in a large population with very low levels of education to determine whether very few years of education could contribute to cognitive reserve and modify the relation of neuropathologic indices to dementia. Methods: In this cross-sectional study, we included 675 individuals 50 years of age or older from the Brazilian Aging Brain Study Group. Cognitive abilities were evaluated through a structured interview with an informant at the time of autopsy, including the Clinical Dementia Rating (CDR) scale. Neuropathologic examinations were performed using immunohistochemistry and following internationally accepted criteria. Multivariate linear regression models were conducted to determine whether the association between cognitive abilities (measured by CDR sum of boxes) and years of education was independent of sociodemographic variables and neuropathologic indices, including neuritic plaques, neurofibrillary tangles, lacunar infarctions, small-vessel disease, and Lewy bodies. In addition, interaction models were used to examine whether education modified the relation between neuropathologic indices and cognition. Results: Mean education was 3.9 ± 3.5 years. Formal education was associated with a lower CDR sum of boxes (β = −0.197; 95% confidence interval −0.343, −0.052; p = 0.008), after adjustment for sociodemographic variables and neuropathologic indices. Furthermore, education modified the relationship of lacunar infarcts with cognitive abilities (p = 0.04). Conclusions: Even a few years of formal education contributes to cognitive reserve.

Post-Mortem diagnosis of dementia by informant interview

Alzheimer’s disease (AD) is characterized by progressive cognitive decline associated with a featured neuropathology (neuritic plaques and neurofibrillary tangles). Several studies have implicated oxidative damage to DNA, DNA repair, and altered cell-cycle regulation in addition to cell death in AD post-mitotic neurons. However, there is a lack of studies that systematically assess those biological processes in patients with AD neuropathology but with no evidence of cognitive impairment. We evaluated markers of oxidative DNA damage (8-OHdG, H2AX), DNA repair (p53, BRCA1, PTEN), and cell-cycle (Cdk1, Cdk4, Cdk5, Cyclin B1, Cyclin D1, p27Kip1, phospho-Rb and E2F1) through immunohistochemistry and cell death through TUNEL in autopsy hippocampal tissue samples arrayed in a tissue microarray (TMA) composed of three groups: I) “clinical-pathological AD” (CP-AD) - subjects with neuropathological AD (Braak≥IV and CERAD = B or C) and clinical dementia (CDR≥2, IQCODE>3.8); II) “pathological AD” (P-AD) - subjects with neuropathological AD (Braak≥IV and CERAD = B or C) and without cognitive impairment (CDR 0, IQCODE<3.2); and III) “normal aging” (N) - subjects without neuropathological AD (Braak≤II and CERAD 0 or A) and with normal cognitive function (CDR 0, IQCODE<3.2). Our results show that high levels of oxidative DNA damage are present in all groups. However, significant reductions in DNA repair and cell-cycle inhibition markers and increases in cell-cycle progression and cell death markers in subjects with CP-AD were detected when compared to both P-AD and N groups, whereas there were no significant differences in the studied markers between P-AD individuals and N subjects. This study indicates that, even in the setting of pathological AD, healthy cognition may be associated with a preserved repair to DNA damage, cell-cycle regulation, and cell death in post-mitotic neurons.

Atherosclerosis and Dementia: A Cross-Sectional Study With Pathological Analysis of the Carotid Arteries

The diagnosis of normal cognition or dementia in the Brazilian Brain Bank of the Aging Brain Study Group (BBBABSG) has relied on postmortem interview with an informant. Objectives To ascertain the sensitivity and specificity of postmortem diagnosis based on informant interview compared against the diagnosis established at a memory clinic. Methods A prospective study was conducted at the BBBABSG and at the Reference Center for Cognitive Disorders (RCCD), a specialized memory clinic of the Hospital das Clínicas, University of São Paulo Medical School. Control subjects and cognitively impaired subjects were referred from the Hospital das Clínicas to the RCCD where subjects and their informants were assessed. The same informant was then interviewed at the BBBABSG. Specialists’ panel consensus, in each group, determined the final diagnosis of the case, blind to other center’s diagnosis. Data was compared for frequency of diagnostic equivalence. For this study, the diagnosis established at the RCCD was accepted as the gold standard. Sensitivity and specificity were computed. Results Ninety individuals were included, 45 with dementia and 45 without dementia (26 cognitively normal and 19 cognitively impaired but non-demented). The informant interview at the BBBABSG had a sensitivity of 86.6% and specificity of 84.4% for the diagnosis of dementia, and a sensitivity of 65.3% and specificity of 93.7% for the diagnosis of normal cognition. Conclusions The informant interview used at the BBBABSG has a high specificity and sensitivity for the diagnosis of dementia as well as a high specificity for the diagnosis of normal cognition.

Assessment of factors that confound MRI and neuropathological correlation of human postmortem brain tissue

Background and Purpose— Previous ultrasound-based studies have shown an association between carotid artery atherosclerosis and dementia. Our aim was to investigate this association using postmortem examination. Methods— Postmortem morphometric measurements of carotid stenosis and intima-media thickness were performed in individuals with dementia (n=112) and control subjects (n=577). Multivariate logistic regression models were applied. Results— High-grade left internal carotid stenosis (≥70%) was associated with increased odds for dementia (OR, 2.30; 95% CI, 1.14–4.74; P=0.02). Intima-media thickness was not associated with dementia. Conclusions— The likelihood of dementia is increased with high-grade left internal carotid artery atherosclerosis after adjusting for demographic and cardiovascular risk factors.

Improved detection of incipient vascular changes by a biotechnological platform combining post mortem MRI in situ with neuropathology

In spite of considerable technical advance in MRI techniques, the optical resolution of these methods are still limited. Consequently, the delineation of cytoarchitectonic fields based on probabilistic maps and brain volume changes, as well as small-scale changes seen in MRI scans need to be verified by neuronanatomical/neuropathological diagnostic tools. To attend the current interdisciplinary needs of the scientific community, brain banks have to broaden their scope in order to provide high quality tissue suitable for neuroimaging- neuropathology/anatomy correlation studies. The Brain Bank of the Brazilian Aging Brain Research Group (BBBABSG) of the University of Sao Paulo Medical School (USPMS) collaborates with researchers interested in neuroimaging-neuropathological correlation studies providing brains submitted to postmortem MRI in-situ. In this paper we describe and discuss the parameters established by the BBBABSG to select and to handle brains for fine-scale neuroimaging-neuropathological correlation studies, and to exclude inappropriate/unsuitable autopsy brains. We tried to assess the impact of the postmortem time and storage of the corpse on the quality of the MRI scans and to establish fixation protocols that are the most appropriate to these correlation studies. After investigation of a total of 36 brains, postmortem interval and low body temperature proved to be the main factors determining the quality of routine MRI protocols. Perfusion fixation of the brains after autopsy by mannitol 20% followed by formalin 20% was the best method for preserving the original brain shape and volume, and for allowing further routine and immunohistochemical staining. Taken to together, these parameters offer a methodological progress in screening and processing of human postmortem tissue in order to guarantee high quality material for unbiased correlation studies and to avoid expenditures by post-imaging analyses and histological processing of brain tissue.

Transcriptional Alterations Related to Neuropathology and Clinical Manifestation of Alzheimer's Disease

The histopathological counterpart of white matter hyperintensities is a matter of debate. Methodological and ethical limitations have prevented this question to be elucidated. We want to introduce a protocol applying state-of-the-art methods in order to solve fundamental questions regarding the neuroimaging-neuropathological uncertainties comprising the most common white matter hyperintensities [WMHs] seen in aging. By this protocol, the correlation between signal features in in situ, post mortem MRI-derived methods, including DTI and MTR and quantitative and qualitative histopathology can be investigated. We are mainly interested in determining the precise neuroanatomical substrate of incipient WMHs. A major issue in this protocol is the exact co-registration of small lesion in a tridimensional coordinate system that compensates tissue deformations after histological processing. The protocol is based on four principles: post mortem MRI in situ performed in a short post mortem interval, minimal brain deformation during processing, thick serial histological sections and computer-assisted 3D reconstruction of the histological sections. This protocol will greatly facilitate a systematic study of the location, pathogenesis, clinical impact, prognosis and prevention of WMHs.