Your browser does not allow saving data (e.g. private mode): bookmarks will be lost when the tab closes.
Search PubMed
Keywords, author, journal, years — results from PubMed, abstracts with Russian translation, bookmarks in your browser.
Found: 5 474
Page 260 of 548-
Ultrastructure of primitive neuroectodermal neoplasms of the central nervous system.
The ultrastructure of one spinal and five cerebral neoplasms diagnosed by light microscopy as primitive neuroectodermal tumors supports a cell population consisting largely of poorly differentiated neuroepithelial cells. The most unique ultrastructure feature was the presence of annulate lamellae in four of the six cases. Glial cells in the neoplasm were not unequivocally of neoplastic origin and were possible reactive. There was no evidence of neuroblastic or neuronal elements, although there was frequently focal early neuroblastic differentiation by light microscopy. Although we have seen neoplasms which are clearly neuroblastic, these particular tumors are not purely neuroblastic and should not be classified as neuroblastomas.
-
Fine structure and permeability of capillaries in the stria vascularis and spiral ligament of the inner ear of the guinea pig.
The blood capillaries in the stria vascularis and the spiral ligaments of guinea pigs were studied by electron microscopy with freeze-fracture and thin section methods, including tracer experiments with horseradish peroxidase (HRP) and microperoxidase (MP). The endothelial cells of the capillaries of both tissues are connected by tight junctions, and contain about the same number of micropinocytotic vesicles. In cases of intravascular administration before fixation, both of the tracers stained the perivascular space and almost all endothelial vesicles in the stria vascularis. On the other hand, the perivascular space and many vesicles in the spinal ligament were unstained. The endothelial tight junctions in the stria vascularis prevented the penetration of HRP, but sometimes allowed the penetration of MP. Those of the spiral ligament were impermeable to both tracers. In cases of tracer administration after fixation, leakage spots of HRP from capillaries were sparsely located all over the stria vascularis. Transendothelial channels and isolated fenestrae formed by micropinocytotic vesicles were detected. It is concluded that the capillaries of the stria vascularis are similar to the muscle capillaries and to the capillaries of the elasmobranch brain, whereas those in the spiral ligament are similar to the brain capillaries of higher vertebrates.
-
Beyond animal models: revolutionizing neurodegenerative disease modeling using 3D in vitro organoids, microfluidic chips, and bioprinting.
Neurodegenerative diseases (NDs) are characterized by uncontrolled loss of neuronal cells leading to a progressive deterioration of brain functions. The transition rate of numerous neuroprotective drugs against Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, leading to FDA approval, is only 8-14% in the last two decades. Thus, in spite of encouraging preclinical results, these drugs have failed in human clinical trials, demonstrating that traditional cell cultures and animal models cannot accurately replicate human pathophysiology. Hence, in vitro three-dimensional (3D) models have been developed to bridge the gap between human and animal studies. Such technological advancements in 3D culture systems, such as human-induced pluripotent stem cell (iPSC)-derived cells/organoids, organ-on-a-chip technique, and 3D bioprinting, have aided our understanding of the pathophysiology and underlying mechanisms of human NDs. Despite these recent advances, we still lack a 3D model that recapitulates all the key aspects of NDs, thus making it difficult to study the ND's etiology in-depth. Hence in this review, we propose developing a combinatorial approach that allows the integration of patient-derived iPSCs/organoids with 3D bioprinting and organ-on-a-chip technique as it would encompass the neuronal cells along with their niche. Such a 3D combinatorial approach would characterize pathological processes thoroughly, making them better suited for high-throughput drug screening and developing effective novel therapeutics targeting NDs.
-
Developmental convergence and divergence in human stem cell models of autism.
Two decades of genetic studies in autism spectrum disorder (ASD) have identified more than 100 genes harbouring rare risk mutations1-13. Despite this substantial heterogeneity, transcriptomic and epigenetic analyses have identified convergent patterns of dysregulation across the ASD postmortem brain14,15-17. To identify shared and distinct mechanisms of ASD-linked mutations, we assembled a large patient collection of human induced pluripotent stem (hiPS) cells, consisting of 70 hiPS cell lines after stringent quality control representing 8 ASD-associated mutations, idiopathic ASD, and 20 lines from non-affected control individuals. Here we used these hiPS cell lines to generate human cortical organoids, profiling by RNA sequencing at four distinct time points up to 100 days after in vitro differentiation. Early time points harboured the largest mutation-specific changes, but different mutations converged on shared transcriptional changes as development progressed. We identified a shared RNA and protein interaction network, which was enriched in ASD risk genes and predicted to drive the observed downstream changes in gene expression. CRISPR-Cas9 screening of these candidate transcriptional regulators in induced human neural progenitors validated their downstream convergent molecular effects. These data illustrate how risk associated with genetically defined forms of ASD can propagate by means of transcriptional regulation to affect convergently dysregulated pathways, providing new insight into the convergent impact of ASD genetic risk on human neurodevelopment.
-
Long-term maturation of human cortical organoids matches key early postnatal transitions.
Human stem-cell-derived models provide the promise of accelerating our understanding of brain disorders, but not knowing whether they possess the ability to mature beyond mid- to late-fetal stages potentially limits their utility. We leveraged a directed differentiation protocol to comprehensively assess maturation in vitro. Based on genome-wide analysis of the epigenetic clock and transcriptomics, as well as RNA editing, we observe that three-dimensional human cortical organoids reach postnatal stages between 250 and 300 days, a timeline paralleling in vivo development. We demonstrate the presence of several known developmental milestones, including switches in the histone deacetylase complex and NMDA receptor subunits, which we confirm at the protein and physiological levels. These results suggest that important components of an intrinsic in vivo developmental program persist in vitro. We further map neurodevelopmental and neurodegenerative disease risk genes onto in vitro gene expression trajectories to provide a resource and webtool (Gene Expression in Cortical Organoids, GECO) to guide disease modeling.
-
Trametinib-mediated MEK inhibition impairs cancer cell viability and invasion in patient-derived tumor avatars of glioblastoma with extraneural metastases: A proof-of-concept study.
Glioblastoma (GBM) remains one of the most lethal human malignancies, yet extraneural metastases are exceptionally rare and poorly understood. Standard treatment-surgical resection followed by chemoradiotherapy-offers only modest survival benefits, and therapeutic options for metastatic GBM are limited. Here, we describe a rare clinical case of metastatic GBM and provide comprehensive molecular characterization alongside a potential targeted treatment strategy. The tumor exhibited several molecular features associated with aggressive behavior, including alterations in the tumor suppressor genes NF1, TP53, PTEN, and RB1, a mesenchymal DNA‑methylation subclass, and activation of the MAPK signaling pathway. To functionally evaluate therapeutic vulnerabilities, we developed tumor models using patient‑derived GBM cells and their assembloids with cerebral organoids that recapitulate patient‑specific tumor biology and the human brain microenvironment. We identified the MEK inhibitor trametinib as a promising candidate capable of selectively reducing viability and invasion of highly aggressive, stem‑like GBM cells within our personalized patient-derived tumor avatars. This work highlights the proof-of-concept evidence that MEK pathway inhibition may represent a potential therapeutic vulnerability to counteract rapid tumor spread and improve responsiveness to temzolomide in this individual metastatic GBM case. Study underscores the need for continued research to advance targeted, multi‑modal therapeutic approaches for GBM.
-
In Vivo Human PSC-Derived Intestinal Organoids to Study Stem Cell Maintenance.
Human intestinal organoids (HIOs), derived from pluripotent stem cells, are a new tool to gain insights in gastrointestinal development, physiology, and associated diseases. Herein, we present a method for renal transplantation of HIOs in immunocompromised mice and subsequent analysis to study intestinal epithelial cell proliferation. In addition, we describe how to generate enteroids from transplanted HIOs. The method highlights the specific steps to successful engraftment and provides insight into the study of human intestinal stem cells.
-
Evidence for rapid structural and functional changes of the melanophore microtubule-organizing center upon pigment movements.
Melanophores of the angelfish, pterophyllum scalare, have previously been shown to display approximately 2,400 microtubules in cells wih pigment dispersed; these microtubules radiate from a presumptive organizing center, the central apparatus (CA), and their number is reduced to approximately 1,000 in the state with aggregated pigment (M. Schliwa and U. Euteneuer, 1978, J. Supramol. Struct. 8:177-190). In an attempt to elucidate the factors controlling this rapid reorganization of the microtubule apparatus, structure and function of the CA have been investigated under different physiological conditions. As a function of the state of pigment distribution, melanophores differ markedly with respect to CA organization. A complex of dense amorphous aggregates and associated fuzzy material, several micrometers in diameter, surrounds the centrioles in cells with pigment dispersed, and numerous microtubules emanate from this complex in a radial fashion. In the aggregated state, on the other hand, few microtubules are observed in the pericentiolar region, and the amount of fibrous material is greatly reduced. These changes in CA morphology as a function of the state of pigment distribution are associated with a marked difference in its capacity to initiatiate the assembly of microtubules from exogenous pure porcine brain tubulin in lysed cell preparations. After complete removal of preexisting microtubules, cells lysed in the dispersed state into a solution of 1-2 mg/ml pure tubulin have numerous microtubules associated with the CA in radial fashion, while cells lysed in the aggregated state nucleate the assembly of only a few microtubules. We conclude that it is the activity of the CA that basically regulates the expression of microtubules. This regulation is achieved through a variation in the capacity to initiate microtubule assembly. Increase or decrease in the amount of dense material, as readily observed in the cell system studied here, seems to be a morphologic expression of such a physiologic function.
-
The pericentriolar material in Chinese hamster ovary cells nucleates microtubule formation.
The structure and function of the centrosomes from Chinese hamster ovary (CHO) cells were investigated by electron microscopy of negatively stained wholemount preparations of cell lysates. Cells were trypsinized from culture dishes, lysed with Triton X-100, sedimented onto ionized, carbon-coated grids, and negatively stained with phosphotungstate. The centrosomes from both interphase and dividing cells consisted of pairs of centrioles, a fibrous pericentriolar material, and a group of virus-like particles which were characteristic of the CHO cells and which served as markers for the pericentriolar material. Interphase centrosomes anchored up to two dozen microtubules when cells were lysed under conditions which preserved native microtubules. When Colcemid-blocked mitotic cells, initially devoid of microtubules, were allowed to recover for 10 min, microtubules formed at the pericentriolar material, but not at the centrioles. When lysates of Colcemid-blocked cells were incubated in vitro with micotubule protein purified from porcine brain tissue, up to 250 microtubules assembled at the centrosomes, similar to the number of microtubules that would normally form at the centrosome during cell division. A few microtubules could also be assembled in vitro onto the ends of isolated centrioles from which the pericentriolar material had been removed, forming characteristic axoneme- like bundles. In addition, microtubules; were assembled onto fragments of densely staining, fibrous material which was tentatively identified as periocentriolar material by its association of CHO can initiate and anchor microtubules both in vivo and in vitro.
-
Patient-derived ependymoma and medulloblastoma tumoroids: generation, biobanking and drug screening.
Ependymoma and medulloblastoma are among the most common malignant pediatric brain tumors and contribute significantly to morbidity and mortality in affected children. Robust models for investigating these tumors' biology and heterogeneity, and exploring alternative therapeutic options, are currently limited. Here we present a detailed protocol for the generation and maintenance of pediatric patient-derived tumoroids (pPDTs) and pediatric patient-derived xenograft tumoroids (pPDXTs) directly from primary ependymoma and medulloblastoma tumor specimens. The protocol extension expands on our previous method for human induced pluripotent stem cell-derived medulloblastoma and high-grade glioma cancer organoids, with which it shares key reagents and methodological steps. This optimized workflow ensures efficient tumoroid establishment, amplification, biobanking, cryopreservation and recovery. In addition, we describe a scalable, low-throughput drug screening approach using calcein-based live-cell staining and automated image analysis, enabling rapid assessment of therapeutic responses. This protocol provides a robust and reproducible platform for modeling pediatric brain tumors in vitro and will enable broader adoption of patient-derived tumoroid systems for mechanistic studies and preclinical drug screening in pediatric neuro-oncology research. The protocol takes 28-35 days for the generation of tumoroids and from 1 to 4 weeks for amplification, biobanking and downstream applications. The protocol requires at least 3-6 months to become proficient in handling patient-derived samples and generating tumoroids.