Distribution of corpora amylacea in the human midbrain: using synchrotron radiation phase-contrast microtomography, high-field magnetic resonance imaging, and histology

Corpora amylacea (CA) are polyglucosan aggregated granules that accumulate in the human body throughout aging. In the cerebrum, CA have been found in proximity to ventricular walls, pial surfaces, and blood vessels. However, studies showing their three-dimensional spatial distribution are sparse. In this study, volumetric images of four human brain stems were obtained with MRI and phase-contrast X-ray microtomography, followed up by Periodic acid Schiff stain for validation. CA appeared as hyperintense spheroid structures with diameters up to 30 μm. An automatic pipeline was developed to segment the CA, and the spatial distribution of over 200,000 individual corpora amylacea could be investigated. A threefold-or higher-density of CA was detected in the dorsomedial column of the periaqueductal gray (860-4,200 CA count/mm3) than in the superior colliculus (150-340 CA count/mm3). We estimated that about 2% of the CA were located in the immediate vicinity of the vessels or in the peri-vascular space. While CA in the ependymal lining of the cerebral aqueduct was rare, the sub-pial tissue of the anterior and posterior midbrain contained several CA. In the sample with the highest CA density, quantitative maps obtained with MRI revealed high R2* values and a diamagnetic shift in a region which spatially coincided with the CA dense region.

Quantitative analysis of size and regional distribution of corpora amylacea in the hippocampal formation of obstructive sleep apnoea patients

Corpora amylacea (CoA) are spherical aggregates of glucose polymers and proteins within the periventricular, perivascular and subpial regions of the cerebral cortex and the hippocampal cornu ammonis (CA) subfields. The present study quantified the distribution of CoA in autopsied hippocampi of patients with obstructive sleep apnoea (OSA) using ethanolamine-induced fluorescence. CoA were observed in 29 of 30 patients (96.7%). They were most abundant in periventricular regions (wall of lateral ventricle, alveus, fimbria and CA4), rarely found in the CA3 and CA1, and undetectable in the CA2 or subiculum. A spatiotemporal sequence of CoA deposition was postulated, beginning in the fimbria and progressively spreading around the subpial layer until they extended medially to the wall of the lateral ventricle and laterally to the collateral sulcus. This ranked CoA sequence was positively correlated with CoA packing density (count and area fraction) and negatively correlated with CoA minimum diameters (p < 0.05). Although this sequence was not correlated with age or body mass index (BMI), age was positively correlated with the mean and maximum diameters of CoA. These findings support the view that the spatiotemporal sequence of CoA deposition is independent of age, and that CoA become larger due to the accretion of new material over time.

Exploring the elusive composition of corpora amylacea of human brain

Corpora amylacea (CA) are polyglucosan bodies that accumulate in the human brain during ageing and are also present in large numbers in neurodegenerative conditions. Theories regarding the function of CA are regularly updated as new components are described. In previous work, we revealed the presence of some neo-epitopes in CA and the existence of some natural IgM antibodies directed against these neo-epitopes. We also noted that these neo-epitopes and IgMs were the cause of false staining in CA immunohistochemical studies, and disproved the proposed presence of β-amyloid peptides and tau protein in them. Here we extend the list of components erroneously attributed to CA. We show that, contrary to previous descriptions, CA do not contain GFAP, S100, AQP4, NeuN or class III β-tubulin, and we question the presence of other components. Nonetheless, we observe that CA contains ubiquitin and p62, both of them associated with processes of elimination of waste substances, and also glycogen synthase, an indispensable enzyme for polyglucosan formation. In summary, this study shows that it is imperative to continue reviewing previous studies about CA but, more importantly, it shows that the vision of CA as structures involved in protective or cleaning mechanisms remains the most consistent theory.

New perspectives on corpora amylacea in the human brain

Corpora amylacea are structures of unknown origin and function that appear with age in human brains and are profuse in selected brain areas in several neurodegenerative conditions. They are constituted of glucose polymers and may contain waste elements derived from different cell types. As we previously found on particular polyglucosan bodies in mouse brain, we report here that corpora amylacea present some neo-epitopes that can be recognized by natural antibodies, a certain kind of antibodies that are involved in tissue homeostasis. We hypothesize that corpora amylacea, and probably some other polyglucosan bodies, are waste containers in which deleterious or residual products are isolated to be later eliminated through the action of the innate immune system. In any case, the presence of neo-epitopes on these structures and the existence of natural antibodies directed against them could become a new focal point for the study of both age-related and degenerative brain processes.

Primary olfactory cortex in autism and epilepsy: increased glial cells in autism

Autism Spectrum Disorder is characterized by sensory anomalies including impaired olfactory identification. Between 5 and 46 percent of individuals with autism have a clinical diagnosis of epilepsy. Primary olfactory cortex (piriform cortex) is central to olfactory identification and is an epileptogenic structure. Cytoarchitectural changes in olfactory cortex may underlie olfactory differences seen in autism. Primary olfactory cortex was sampled from 17 post-mortem autism cases with and without epilepsy, 11 epilepsy cases without autism and 11 typically developed cases. Stereological and neuropathological methods were used to quantify glial, pyramidal and non-pyramidal cell densities in layers of the piriform as well as identify pathological differences in this area and its neighbouring region, the olfactory tubercle. We found increased layer II glial cell densities in autism with and without epilepsy, which were negatively correlated with age and positively correlated with levels of corpora amylacea in layer I. These changes were also associated with greater symptom severity and did not extend to the olfactory tubercle. Glial cell organization may follow an altered trajectory of development with age in autism. The findings are consistent with other studies implicating increased glial cells in the autism brain. Altered cytoarchitecture may contribute to sensory deficits observed in affected individuals. This study provides evidence that autism is linked to alterations in the cytoarchitectural structure that underlies primary sensory processes and is not restricted to heteromodal ("higher") cognitive centers.

Discovering the Structure of Nerve Tissue: Part 2: Gabriel Valentin, Robert Remak, and Jan Evangelista Purkyně

During the 1830s, the use of improved microscopic techniques together with new histological methods, including tissue fixation, allowed more precise data to be obtained concerning the structure of nerve tissue of animals as well as humans. The present article, based on the translations of original texts never before published, brings together for the first time the discoveries of famous scholars Gustav Valentin, Robert Remak, and Jan Evangelista Purkyně, who made their significant discoveries in the field of neuroscience almost simultaneously and shows how their findings affected each other. In addition, this article also contains digitally remastered and reconstructed figures published in the original works of Valentin, Remak, and Purkyně and they are displayed for the first time in high quality. Although the fundamental discoveries of these famous scholars did not imply the discovery of nerve cells as we know them today, they were certainly a very important basis for further research of many other eminent scholars during the second half of the nineteenth century.