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Page 156 of 547-
Melatonin Rescues the Dendrite Collapse Induced by the Pro-Oxidant Toxin Okadaic Acid in Organotypic Cultures of Rat Hilar Hippocampus.
The pro-oxidant compound okadaic acid (OKA) mimics alterations found in Alzheimer's disease (AD) as oxidative stress and tau hyperphosphorylation, leading to neurodegeneration and cognitive decline. Although loss of dendrite complexity occurs in AD, the study of this post-synaptic domain in chemical-induced models remains unexplored. Moreover, there is a growing expectation for therapeutic adjuvants to counteract these brain dysfunctions. Melatonin, a free-radical scavenger, inhibits tau hyperphosphorylation, modulates phosphatases, and strengthens dendritic arbors. Thus, we determined if OKA alters the dendritic arbors of hilar hippocampal neurons and whether melatonin prevents, counteracts, or reverses these damages. Rat organotypic cultures were incubated with vehicle, OKA, melatonin, and combined treatments with melatonin either before, simultaneously, or after OKA. DNA breaks were assessed by TUNEL assay and nuclei were counterstained with DAPI. Additionally, MAP2 was immunostained to assess the dendritic arbor properties by the Sholl method. In hippocampal hilus, OKA increased DNA fragmentation and reduced the number of MAP2(+) cells, whereas melatonin protected against oxidation and apoptosis. Additionally, OKA decreased the dendritic arbor complexity and melatonin not only counteracted, but also prevented and reversed the dendritic arbor retraction, highlighting its role in post-synaptic domain integrity preservation against neurodegenerative events in hippocampal neurons.
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Evidence for the presence of two 24-h rhythms 180 degrees out of phase in the pineal gland of male Pirbright-White guinea pigs as monitored by counting "synaptic" ribbons and spherules.
Previous studies have shown that the "synaptic" bodies of mammalian pinealocytes are a heterogeneous group of organelles. Whereas "synaptic" ribbons (SR) exhibit a day/night rhythm with small numbers during daytime and high numbers at night, the so-called "synaptic" spherules (SS) show species-specific differences in their rhythmicity. In the present study the numbers of SR and SS were monitored in male guinea pigs over a full 24-h period at 4-hourly intervals (LD 12:12, lights on at 7:00). The results obtained show that the rhythms of SR numbers and SS numbers are out of phase by 180 degrees. SR numbers are small during daytime and high at night, whereas SS numbers are high during daytime and low at night. As there are no indications that SR are transformed into SS and vice versa and as SR and SS lie in different parenchymal areas it is suggested that they characterize different types of pinealocytes with differing rhythmicities. - Serum melatonin levels were low during daytime (30 pg/ml) and increased at night to reach a peak (84 pg/ml) at 24:00 h.
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Protocol for recording of neural activity in 3D midbrain organoids using a multiple-electrode array.
Here, we present a protocol for electrophysiological recording from human three-dimensional (3D) organoids using substrates designed for two-dimensional cultures. We describe steps for generating midbrain 3D organoids from human induced pluripotent stem cells (hiPSCs) utilizing 6-well multi-electrode array (MEA) plates. We then detail procedures for recording neuronal activity via the neural module for Axion Maestro system. Our approach provides neural recording in organoids with high reliability and reproducibility, opening new avenues for research into human neurodevelopment and disease modeling.
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Telencephalon Organoids Derived from an Individual with ADHD Show Altered Neurodevelopment of Early Cortical Layer Structure.
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that occurs in early childhood and can persist to adulthood. It can affect many aspects of a patient's daily life, so it is necessary to explore the mechanism and pathological alterations. For this purpose, we applied induced pluripotent stem cell (iPSC)-derived telencephalon organoids to recapitulate the alterations occurring in the early cerebral cortex of ADHD patients. We found that telencephalon organoids of ADHD showed less growth of layer structures than control-derived organoids. On day 35 of differentiation, the thinner cortex layer structures of ADHD-derived organoids contained more neurons than those of control-derived organoids. Furthermore, ADHD-derived organoids showed a decrease in cell proliferation during development from day 35 to 56. On day 56 of differentiation, there was a significant difference in the proportion of symmetric and asymmetric cell division between the ADHD and control groups. In addition, we observed increased cell apoptosis in ADHD during early development. These results show alterations in the characteristics of neural stem cells and the formation of layer structures, which might indicate key roles in the pathogenesis of ADHD. Our organoids exhibit the cortical developmental alterations observed in neuroimaging studies, providing an experimental foundation for understanding the pathological mechanisms of ADHD.
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Centriole migration.
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The mode of migration of neurons to the hippocampus: a Golgi and electron microscopic analysis in foetal rhesus monkey.
The mode of neuron migration from the site of their origin in the ventricular zone to area CA1 of the hippocampus was analysed with Golgi and electron microscopic methods during the first half of gestation in the foetal rhesus monkey. In the inner portion of the intermediate zone, the migrating cells have a bipolar form with one, or oaccasionally two, leading processes which do not reach the ammonic plate and with a single trailing process which usually ends within the intermediate zone. Both the nucleus and the cytoplasm of the migrating cells are relatively electron-dense and the latter contains organelles typical of young neurons as described in other brain regions. Analysis of electron micrographs from serial sections reveals that the length of the somata and of the leading and trailing processes of the migrating neurons is apposed to fascicles of radially oriented, electron-lucent, microtubule-filled fibres which are ultrastructurally similar to the radial glial fibres of the neocortex and to the Bergmann glial fibres of the cerebellum. The close (20 nm) apposition between the membranes of the migrating cell and the radial fibre is maintained even in areas where the fibres bend or curve tortuously. Migrating neurons situated at progressively more superficial levels of the intermediate zone become progressively more differentiated and complex. Thus, in the outer portion of the intermediate zone, the migrating cells acquire several additional cytoplasmic processes and occasionally a long thin axon-like process which courses into the incipient alveus. These cells have somewhat larger somata and less electron-dense nuclei and cytoplasm than the migrating neurons still situated in the inner part of the intermediate zone. Cells close to the ammonic plate usually have one to three cytoplasmic processes that enter the ammonic plate and terminate near their presumed final position. Migrating neurons situated at the lower border of the ammonic plate have a single large apical process which intermingles with neurons already in their final position and which sometimes traverses the ammonic plate. The apposition of the migrating neurons to the radial glial processes becomes less explicit as the cell soma enters the ammonic plate, reflecting the more complex three-dimensional intercellular relationships. However, the present analysis indicates that during the middle and late stages of neuronal migration to the hippocampus radial glial fibres may guide postmitotic young neurons across the intermediate zone to the ammonic plate in the same way that they guide neurons migrating to the superficial and middle layers of the neocortical plate.
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Patient-derived forebrain cortical organoids reveal biphasic tau-MAP6-microtubule axis dysfunction in tauopathy.
INTRODUCTION: In frontotemporal dementia (FTD), tau detaches from axonal microtubules and forms pathological aggregates. Rather than stabilizing microtubules, tau promotes labile microtubule domains, redefining its role in neurodegeneration and underscoring the need for human models that capture temporal disease progression. METHODS: Human induced pluripotent stem cells carrying MAPTWT/P301L, MAPTWT/P301S, or MAPTWT/R406W mutations and isogenic controls were differentiated into forebrain cortical organoids (1 to 8 months). Tau isoforms, microtubule dynamics, MAP6 regulation, neuronal activity, tau mRNA stability, and tau pathology were analyzed using biochemical, imaging, and electrophysiological approaches, some of which were benchmarked to postmortem behavorial variant FTD cortex. RESULTS: Early-phase tau mutant organoids showed elevated tau, hyperdynamic microtubules, and neuronal hyperexcitability, partially reversible by tau reduction. Late-phase organoids exhibited insoluble tau accumulation, microtubule hyperstability, and neurodegeneration and reactive astrocytes, accompanied by opposing, phase-dependent MAP6 changes. DISCUSSION: This work reveals a biphasic tau-MAP6-microtubule mechanism driving tauopathy and establishes these organoids as a platform for phase-specific therapy.
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Ultrastructural studies of the dying-back process. II. The sequestration and removal by Schwann cells and oligodendrocytes of organelles from normal and diseases axons.
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Assessment of the broad-spectrum host targeting antiviral efficacy of halofuginone hydrobromide in human airway, intestinal and brain organotypic models.
Halofuginone hydrobromide has shown potent antiviral efficacy against a variety of viruses such as SARS-CoV-2, dengue, or chikungunya virus, and has, therefore, been hypothesized to have broad-spectrum antiviral activity. In this paper, we tested this broad-spectrum antiviral activity of Halofuginone hydrobomide against viruses from different families (Picornaviridae, Herpesviridae, Orthomyxoviridae, Coronaviridae, and Flaviviridae). To this end, we used relevant human models of the airway and intestinal epithelium and regionalized neural organoids. Halofuginone hydrobomide showed antiviral activity against SARS-CoV-2 in the airway epithelium with no toxicity at equivalent concentrations used in human clinical trials but not against any of the other tested viruses.
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Lycium barbarum glycopeptide ameliorates aberrant neuronal activity via ER stress modulation in ventral forebrain organoids derived from depressive patients.
Major depressive disorder (MDD) is a debilitating psychiatric condition associated with substantial personal, societal, and economic costs. Despite considerable advances in research, most conventional antidepressant therapies fail to achieve adequate response in a significant proportion of patients, underscoring the need for novel, mechanism-based interventions. Lycium barbarum glycopeptide (LbGp), a bioactive compound with emerging neuroprotective properties, has been proposed as a candidate for antidepressant development; however, its therapeutic efficacy and underlying mechanisms remain largely uncharacterized. In this study, ventral forebrain organoids were generated from patients with MDD to investigate disease-related neurophysiological abnormalities. These organoids exhibited disrupted neuronal morphology, diminished calcium signaling, and impaired electrophysiological activity. Administration of LbGp effectively restored structural and functional deficits in MDD-derived organoids. Transcriptomic profiling revealed that LbGp ameliorated endoplasmic reticulum (ER) stress responses. To investigate the causative role of ER stress, control organoids were treated with the ER stress agonist CCT020312, which elicited neural activity impairments resembling those observed in MDD organoids. Notably, LbGp reversed the phenotypic consequences of CCT020312 exposure in control organoids. In conclusion, ventral forebrain organoids derived from individuals with MDD demonstrated that LbGp ameliorates disease-associated phenotypes by modulating ER stress.