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Page 133 of 547-
[Ultrastructure of hem- angioblastomas of the central nervous system].
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A technique for improved fixation of the pigeon central nervous system for electron microscopy.
The central nervous system (CNS) of the pigeon has been difficult to fix with consistency, and consequently this problem has impeded ultrastructural studies of various parts of the pigeon brain. Here we describe a method for effective fixation of the pigeon CNS and discuss the three principal problems associated with good fixation of this animal's brain. The animal was deeply anesthetized and the thoracic cavity was opened without collapsing the pectoral girdle upon the brachiocephalic trunks and the common carotids. The perfusion pressure was raised to 140-150 mm Hg to overcome the high resistance of the small diameter, long common carotids. Heparin was added to the wash buffer to retard coagulation of blood in the vascular bed of the brain. The method is not foolproof, but with care excellent fixation can be achieved.
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A new synaptic specialization: filamentous braids.
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A cis-acting structural variation at the ZNF558 locus controls a gene regulatory network in human brain development.
The human forebrain has expanded in size and complexity compared to chimpanzees despite limited changes in protein-coding genes, suggesting that gene expression regulation is an important driver of brain evolution. Here, we identify a KRAB-ZFP transcription factor, ZNF558, that is expressed in human but not chimpanzee forebrain neural progenitor cells. ZNF558 evolved as a suppressor of LINE-1 transposons but has been co-opted to regulate a single target, the mitophagy gene SPATA18. ZNF558 plays a role in mitochondrial homeostasis, and loss-of-function experiments in cerebral organoids suggests that ZNF558 influences developmental timing during early human brain development. Expression of ZNF558 is controlled by the size of a variable number tandem repeat that is longer in chimpanzees compared to humans, and variable in the human population. Thus, this work provides mechanistic insight into how a cis-acting structural variation establishes a regulatory network that affects human brain evolution.
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Inflammatory Response and Exosome Biogenesis of Choroid Plexus Organoids Derived from Human Pluripotent Stem Cells.
The choroid plexus (ChP) is a complex structure in the human brain that is responsible for the secretion of cerebrospinal fluid (CSF) and forming the blood-CSF barrier (B-CSF-B). Human-induced pluripotent stem cells (hiPSCs) have shown promising results in the formation of brain organoids in vitro; however, very few studies to date have generated ChP organoids. In particular, no study has assessed the inflammatory response and the extracellular vesicle (EV) biogenesis of hiPSC-derived ChP organoids. In this study, the impacts of Wnt signaling on the inflammatory response and EV biogenesis of ChP organoids derived from hiPSCs was investigated. During days 10-15, bone morphogenetic protein 4 was added along with (+/-) CHIR99021 (CHIR, a small molecule GSK-3β inhibitor that acts as a Wnt agonist). At day 30, the ChP organoids were characterized by immunocytochemistry and flow cytometry for TTR (~72%) and CLIC6 (~20%) expression. Compared to the -CHIR group, the +CHIR group showed an upregulation of 6 out of 10 tested ChP genes, including CLIC6 (2-fold), PLEC (4-fold), PLTP (2-4-fold), DCN (~7-fold), DLK1 (2-4-fold), and AQP1 (1.4-fold), and a downregulation of TTR (0.1-fold), IGFBP7 (0.8-fold), MSX1 (0.4-fold), and LUM (0.2-0.4-fold). When exposed to amyloid beta 42 oligomers, the +CHIR group had a more sensitive response as evidenced by the upregulation of inflammation-related genes such as TNFα, IL-6, and MMP2/9 when compared to the -CHIR group. Developmentally, the EV biogenesis markers of ChP organoids showed an increase over time from day 19 to day 38. This study is significant in that it provides a model of the human B-CSF-B and ChP tissue for the purpose of drug screening and designing drug delivery systems to treat neurological disorders such as Alzheimer's disease and ischemic stroke.
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[Subcellular reaction to cerebral hypoxia].
Compensatory-adaptive reaction of the brain to hypoxia depends on destructive and reparative processes developing in neuronal and glial elements. A drastic tension and reconstruction of the energy apparatus--mitochondria occurs, as well as reversible disturbances in informative connections between the nucleus and cytoplasm and between nerve fibers and synapses. As a result, structural-functional activity of organells decreases along with changes in metabolic processes. Destructive processes in oligodendroglia, at all stages of the experiment, are more pronounced than in neurons. Preliminary injection of hydroxybutyric acid to the animals preserves the cellular energy potential under hypoxia, that is evident from the lack of severe alterations in mitochondria and other organells. Mechanisms of the adaptive-compensatory reaction in cortical neurons under hypoxia are connected with tension and reconstruction of all organells of the brain cellular elements and with biochemical shifts of lactate dehydrogenase enzymes.
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A comparative ultrastructural study of the low virulent strain PV-C1/81 and RH strain cultured in A9, Vero, SIRC cell lines.
A human Toxoplasma strain, isolated in mice from bioptic lymphoglandular tissue, has been cultured in vitro in continuous cell lines. Its presence in some parastized cells, with parasitophorous vacuoles surrounded by a cyst-like wall and filled with a cystozoite-like clone, was observed by electron microscopy. These characteristic and constant features were confined in different cell line cultures and are suggested as possible markers of low virulent strains.
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Regulation of the in vivo mitotic apparatus by glycols and metabolic inhibitors.
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Recreating the blood-CNS barrier in vitro.
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Histofluorescence and ultrastructural evidence for catecholamine-containing sensory neurons bordering the interventricular foramen of the toad brain.