Renata Elaine Paraizo Leite

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.

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.

Transcriptomic analysis of purified human cortical microglia reveals age-associated changes

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.

Cell number changes in Alzheimer's disease relate to dementia, not to plaques and tangles.

Microglia are essential for CNS homeostasis and innate neuroimmune function, and play important roles in neurodegeneration and brain aging. Here we present gene expression profiles of purified microglia isolated at autopsy from the parietal cortex of 39 human subjects with intact cognition. Overall, genes expressed by human microglia were similar to those in mouse, including established microglial genes CX3CR1, P2RY12 and ITGAM (CD11B). However, a number of immune genes, not identified as part of the mouse microglial signature, were abundantly expressed in human microglia, including TLR, Fcγ and SIGLEC receptors, as well as TAL1 and IFI16, regulators of proliferation and cell cycle. Age-associated changes in human microglia were enriched for genes involved in cell adhesion, axonal guidance, cell surface receptor expression and actin (dis)assembly. Limited overlap was observed in microglial genes regulated during aging between mice and humans, indicating that human and mouse microglia age differently.

d-serine levels in Alzheimer's disease: implications for novel biomarker development.

Alzheimers disease is the commonest cause of dementia in the elderly, but its pathological determinants are still debated. Amyloid-β plaques and neurofibrillary tangles have been implicated either directly as disruptors of neural function, or indirectly by precipitating neuronal death and thus causing a reduction in neuronal number. Alternatively, the initial cognitive decline has been attributed to subtle intracellular events caused by amyloid-β oligomers, resulting in dementia after massive synaptic dysfunction followed by neuronal degeneration and death. To investigate whether Alzheimers disease is associated with changes in the absolute cell numbers of ageing brains, we used the isotropic fractionator, a novel technique designed to determine the absolute cellular composition of brain regions. We investigated whether plaques and tangles are associated with neuronal loss, or whether it is dementia that relates to changes of absolute cell composition, by comparing cell numbers in brains of patients severely demented with those of asymptomatic individuals-both groups histopathologically diagnosed as Alzheimers-and normal subjects with no pathological signs of the disease. We found a great reduction of neuronal numbers in the hippocampus and cerebral cortex of demented patients with Alzheimers disease, but not in asymptomatic subjects with Alzheimers disease. We concluded that neuronal loss is associated with dementia and not the presence of plaques and tangles, which may explain why subjects with histopathological features of Alzheimers disease can be asymptomatic; and exclude amyloid-β deposits as causes for the reduction of neuronal numbers in the brain. We found an increase of non-neuronal cell numbers in the cerebral cortex and subcortical white matter of demented patients with Alzheimers disease when compared with asymptomatic subjects with Alzheimers disease and control subjects, suggesting a reactive glial cell response in the former that may be related to the symptoms they present.

The human cerebral cortex is neither one nor many: neuronal distribution reveals two quantitatively different zones in the gray matter, three in the white matter, and explains local variations in cortical folding

Alzheimer’s disease (AD) is a severe neurodegenerative disorder still in search of effective methods of diagnosis. Altered levels of the NMDA receptor co-agonist, d-serine, have been associated with neurological disorders, including schizophrenia and epilepsy. However, whether d-serine levels are deregulated in AD remains elusive. Here, we first measured D-serine levels in post-mortem hippocampal and cortical samples from nondemented subjects (n=8) and AD patients (n=14). We next determined d-serine levels in experimental models of AD, including wild-type rats and mice that received intracerebroventricular injections of amyloid-β oligomers, and APP/PS1 transgenic mice. Finally, we assessed d-serine levels in the cerebrospinal fluid (CSF) of 21 patients with a diagnosis of probable AD, as compared with patients with normal pressure hydrocephalus (n=9), major depression (n=9) and healthy controls (n=10), and results were contrasted with CSF amyloid-β/tau AD biomarkers. d-serine levels were higher in the hippocampus and parietal cortex of AD patients than in control subjects. Levels of both d-serine and serine racemase, the enzyme responsible for d-serine production, were elevated in experimental models of AD. Significantly, d-serine levels were higher in the CSF of probable AD patients than in non-cognitively impaired subject groups. Combining d-serine levels to the amyloid/tau index remarkably increased the sensitivity and specificity of diagnosis of probable AD in our cohort. Our results show that increased brain and CSF d-serine levels are associated with AD. CSF d-serine levels discriminated between nondemented and AD patients in our cohort and might constitute a novel candidate biomarker for early AD diagnosis.

Effects of a non-focal plasticity protocol on apathy in moderate Alzheimer's disease: a randomized, double-blind, sham-controlled trial.

The human prefrontal cortex has been considered different in several aspects and relatively enlarged compared to the rest of the cortical areas. Here we determine whether the white and gray matter of the prefrontal portion of the human cerebral cortex have similar or different cellular compositions relative to the rest of the cortical regions by applying the Isotropic Fractionator to analyze the distribution of neurons along the entire anteroposterior axis of the cortex, and its relationship with the degree of gyrification, number of neurons under the cortical surface, and other parameters. The prefrontal region shares with the remainder of the cerebral cortex (except for occipital cortex) the same relationship between cortical volume and number of neurons. In contrast, both occipital and prefrontal areas vary from other cortical areas in their connectivity through the white matter, with a systematic reduction of cortical connectivity through the white matter and an increase of the mean axon caliber along the anteroposterior axis. These two parameters explain local differences in the distribution of neurons underneath the cortical surface. We also show that local variations in cortical folding are neither a function of local numbers of neurons nor of cortical thickness, but correlate with properties of the white matter, and are best explained by the folding of the white matter surface. Our results suggest that the human cerebral cortex is divided in two zones (occipital and non-occipital) that differ in how neurons are distributed across their gray matter volume and in three zones (prefrontal, occipital, and non-occipital) that differ in how neurons are connected through the white matter. Thus, the human prefrontal cortex has the largest fraction of neuronal connectivity through the white matter and the smallest average axonal caliber in the white matter within the cortex, although its neuronal composition fits the pattern found for other, non-occipital areas.

Locus coeruleus volume and cell population changes during Alzheimer's disease progression: A stereological study in human postmortem brains with potential implication for early-stage biomarker discovery.

BACKGROUND Apathy is the most common neuropsychiatric symptom in Alzheimers disease (AD) and it is associated with changes in prefrontal neural circuits involved with generation of voluntary actions. To date no effective treatment for apathy has been demonstrated. OBJECTIVE We aimed to investigate the effects and safety of repetitive transcranial direct current stimulation (tDCS) on apathy in moderate AD patients. METHODS Forty patients were randomized to receive either active or sham-tDCS over the left dorsolateral prefrontal cortex (DLPFC). Patients received six sessions of intervention during 2 weeks and were evaluated at baseline, at week 1 and 2, and after 1 week without intervention. Clinical raters, patients, and caregivers were blinded. The primary outcome was apathy. Global cognition and neuropsychiatric symptoms were examined as secondary outcomes. RESULTS The mean MMSE score at baseline was 15.2 ± 2.9 and the mean Apathy Scale score was 27.7 ± 6.7. Changes on apathy scores over time were not different between active and sham tDCS (P = 0.552 for repeated measures). Further analyses confirm that changes from baseline did not differ between groups after the sixth session (active tDCS -1.95 (95%CI -3.49, -0.41); sham-tDCS -2.05 (95%CI -3.68, -0.42); P = 0.989]. Similarly, tDCS had no effect on secondary outcomes (P > 0.40). tDCS was well tolerated and not associated with significant adverse effects. CONCLUSION In this adequately powered study for minimal clinically significant difference, our findings show that using the parameters we chose for this study, repeated anodal tDCS over the left DLPFC had no effect on apathy in elderly patients with moderate AD.

Sexual Dimorphism in the Human Olfactory Bulb: Females Have More Neurons and Glial Cells than Males

Alzheimers disease (AD) progression follows a specific spreading pattern, emphasizing the need to characterize those brain areas that degenerate first. The brainstems locus coeruleus (LC) is the first area to develop neurofibrillary changes (neurofibrillary tangles [NFTs]).