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Neural Stem Cells: Self-renewing cells that generate the main phenotypes of the nervous system in both the embryo and adult. Neural stem cells are precursors to both NEURONS and NEUROGLIA.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.Adult Stem Cells: Cells with high proliferative and self renewal capacities derived from adults.Stem Cell Transplantation: The transfer of STEM CELLS from one individual to another within the same species (TRANSPLANTATION, HOMOLOGOUS) or between species (XENOTRANSPLANTATION), or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS). The source and location of the stem cells determines their potency or pluripotency to differentiate into various cell types.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Embryonic Stem Cells: Cells derived from the BLASTOCYST INNER CELL MASS which forms before implantation in the uterine wall. They retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.Neurogenesis: Formation of NEURONS which involves the differentiation and division of STEM CELLS in which one or both of the daughter cells become neurons.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Nestin: A type VI intermediate filament protein expressed mostly in nerve cells where it is associated with the survival, renewal and mitogen-stimulated proliferation of neural progenitor cells.Stem Cell Niche: A particular zone of tissue composed of a specialized microenvironment where stem cells are retained in a undifferentiated, self-renewable state.Multipotent Stem Cells: Specialized stem cells that are committed to give rise to cells that have a particular function; examples are MYOBLASTS; MYELOID PROGENITOR CELLS; and skin stem cells. (Stem Cells: A Primer [Internet]. Bethesda (MD): National Institutes of Health (US); 2000 May [cited 2002 Apr 5]. Available from: http://www.nih.gov/news/stemcell/primer.htm)Hematopoietic Stem Cells: Progenitor cells from which all blood cells derive.Lateral Ventricles: Cavity in each of the CEREBRAL HEMISPHERES derived from the cavity of the embryonic NEURAL TUBE. They are separated from each other by the SEPTUM PELLUCIDUM, and each communicates with the THIRD VENTRICLE by the foramen of Monro, through which also the choroid plexuses (CHOROID PLEXUS) of the lateral ventricles become continuous with that of the third ventricle.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Cell Lineage: The developmental history of specific differentiated cell types as traced back to the original STEM CELLS in the embryo.Pluripotent Stem Cells: Cells that can give rise to cells of the three different GERM LAYERS.Fetal Stem Cells: Cells derived from a FETUS that retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.Induced Pluripotent Stem Cells: Cells from adult organisms that have been reprogrammed into a pluripotential state similar to that of EMBRYONIC STEM CELLS.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Ependyma: A thin membrane that lines the CEREBRAL VENTRICLES and the central canal of the SPINAL CORD.Intermediate Filament Proteins: Filaments 7-11 nm in diameter found in the cytoplasm of all cells. Many specific proteins belong to this group, e.g., desmin, vimentin, prekeratin, decamin, skeletin, neurofilin, neurofilament protein, and glial fibrillary acid protein.SOXB1 Transcription Factors: A subclass of SOX transcription factors that are expressed in neuronal tissue where they may play a role in the regulation of CELL DIFFERENTIATION. Members of this subclass are generally considered to be transcriptional activators.Hematopoietic Stem Cell Transplantation: Transfer of HEMATOPOIETIC STEM CELLS from BONE MARROW or BLOOD between individuals within the same species (TRANSPLANTATION, HOMOLOGOUS) or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS). Hematopoietic stem cell transplantation has been used as an alternative to BONE MARROW TRANSPLANTATION in the treatment of a variety of neoplasms.Astrocytes: A class of large neuroglial (macroglial) cells in the central nervous system - the largest and most numerous neuroglial cells in the brain and spinal cord. Astrocytes (from "star" cells) are irregularly shaped with many long processes, including those with "end feet" which form the glial (limiting) membrane and directly and indirectly contribute to the BLOOD-BRAIN BARRIER. They regulate the extracellular ionic and chemical environment, and "reactive astrocytes" (along with MICROGLIA) respond to injury.Neuroglia: The non-neuronal cells of the nervous system. They not only provide physical support, but also respond to injury, regulate the ionic and chemical composition of the extracellular milieu, participate in the BLOOD-BRAIN BARRIER and BLOOD-RETINAL BARRIER, form the myelin insulation of nervous pathways, guide neuronal migration during development, and exchange metabolites with neurons. Neuroglia have high-affinity transmitter uptake systems, voltage-dependent and transmitter-gated ion channels, and can release transmitters, but their role in signaling (as in many other functions) is unclear.Nerve Tissue ProteinsCerebral Ventricles: Four CSF-filled (see CEREBROSPINAL FLUID) cavities within the cerebral hemispheres (LATERAL VENTRICLES), in the midline (THIRD VENTRICLE) and within the PONS and MEDULLA OBLONGATA (FOURTH VENTRICLE).Mesenchymal Stromal Cells: Bone-marrow-derived, non-hematopoietic cells that support HEMATOPOETIC STEM CELLS. They have also been isolated from other organs and tissues such as UMBILICAL CORD BLOOD, umbilical vein subendothelium, and WHARTON JELLY. These cells are considered to be a source of multipotent stem cells because they include subpopulations of mesenchymal stem cells.Mesenchymal Stem Cell Transplantation: Transfer of MESENCHYMAL STEM CELLS between individuals within the same species (TRANSPLANTATION, HOMOLOGOUS) or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS).Spheroids, Cellular: Spherical, heterogeneous aggregates of proliferating, quiescent, and necrotic cells in culture that retain three-dimensional architecture and tissue-specific functions. The ability to form spheroids is a characteristic trait of CULTURED TUMOR CELLS derived from solid TUMORS. Cells from normal tissues can also form spheroids. They represent an in-vitro model for studies of the biology of both normal and malignant cells. (From Bjerkvig, Spheroid Culture in Cancer Research, 1992, p4)Telencephalon: The anterior subdivision of the embryonic PROSENCEPHALON or the corresponding part of the adult prosencephalon that includes the cerebrum and associated structures.Cell Culture Techniques: Methods for maintaining or growing CELLS in vitro.Neoplastic Stem Cells: Highly proliferative, self-renewing, and colony-forming stem cells which give rise to NEOPLASMS.Oligodendroglia: A class of large neuroglial (macroglial) cells in the central nervous system. Oligodendroglia may be called interfascicular, perivascular, or perineuronal (not the same as SATELLITE CELLS, PERINEURONAL of GANGLIA) according to their location. They form the insulating MYELIN SHEATH of axons in the central nervous system.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Prosencephalon: The anterior of the three primitive cerebral vesicles of the embryonic brain arising from the NEURAL TUBE. It subdivides to form DIENCEPHALON and TELENCEPHALON. (Stedmans Medical Dictionary, 27th ed)Bromodeoxyuridine: A nucleoside that substitutes for thymidine in DNA and thus acts as an antimetabolite. It causes breaks in chromosomes and has been proposed as an antiviral and antineoplastic agent. It has been given orphan drug status for use in the treatment of primary brain tumors.Stem Cell Factor: A hematopoietic growth factor and the ligand of the cell surface c-kit protein (PROTO-ONCOGENE PROTEINS C-KIT). It is expressed during embryogenesis and is a growth factor for a number of cell types including the MAST CELLS and the MELANOCYTES in addition to the HEMATOPOIETIC STEM CELLS.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Mice, Inbred C57BLImmunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Cell Movement: The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.Glial Fibrillary Acidic Protein: An intermediate filament protein found only in glial cells or cells of glial origin. MW 51,000.Receptors, Notch: A family of conserved cell surface receptors that contain EPIDERMAL GROWTH FACTOR repeats in their extracellular domain and ANKYRIN repeats in their cytoplasmic domains. The cytoplasmic domain of notch receptors is released upon ligand binding and translocates to the CELL NUCLEUS where it acts as transcription factor.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Octamer Transcription Factor-3: An octamer transcription factor that is expressed primarily in totipotent embryonic STEM CELLS and GERM CELLS and is down-regulated during CELL DIFFERENTIATION.Cell Survival: The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.Dentate Gyrus: GRAY MATTER situated above the GYRUS HIPPOCAMPI. It is composed of three layers. The molecular layer is continuous with the HIPPOCAMPUS in the hippocampal fissure. The granular layer consists of closely arranged spherical or oval neurons, called GRANULE CELLS, whose AXONS pass through the polymorphic layer ending on the DENDRITES of PYRAMIDAL CELLS in the hippocampus.Cell SeparationGreen Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.Cell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Stem Cell Research: Experimentation on STEM CELLS and on the use of stem cells.Olfactory Bulb: Ovoid body resting on the CRIBRIFORM PLATE of the ethmoid bone where the OLFACTORY NERVE terminates. The olfactory bulb contains several types of nerve cells including the mitral cells, on whose DENDRITES the olfactory nerve synapses, forming the olfactory glomeruli. The accessory olfactory bulb, which receives the projection from the VOMERONASAL ORGAN via the vomeronasal nerve, is also included here.Brain Neoplasms: Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain.Totipotent Stem Cells: Single cells that have the potential to form an entire organism. They have the capacity to specialize into extraembryonic membranes and tissues, the embryo, and all postembryonic tissues and organs. (Stem Cells: A Primer [Internet]. Bethesda (MD): National Institutes of Health (US); 2000 May [cited 2002 Apr 5]. Available from: http://www.nih.gov/news/stemcell/primer.htm)Plant Stems: Parts of plants that usually grow vertically upwards towards the light and support the leaves, buds, and reproductive structures. (From Concise Dictionary of Biology, 1990)Basic Helix-Loop-Helix Transcription Factors: A family of DNA-binding transcription factors that contain a basic HELIX-LOOP-HELIX MOTIF.Nervous System: The entire nerve apparatus, composed of a central part, the brain and spinal cord, and a peripheral part, the cranial and spinal nerves, autonomic ganglia, and plexuses. (Stedman, 26th ed)Central Nervous System: The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.Neuroepithelial Cells: Cells of epithelial origin possessing specialized sensory functions. They include cells that are found in the TASTE BUDS; OLFACTORY MUCOSA; COCHLEA; and NEUROEPITHELIAL BODIES.Regeneration: The physiological renewal, repair, or replacement of tissue.Cell Tracking: Non-invasive imaging of cells that have been labeled non-destructively, such as with nanoemulsions or reporter genes that can be detected by molecular imaging, to monitor their location, viability, cell lineage expansion, response to drugs, movement, or other behaviors in vivo.Regenerative Medicine: A field of medicine concerned with developing and using strategies aimed at repair or replacement of damaged, diseased, or metabolically deficient organs, tissues, and cells via TISSUE ENGINEERING; CELL TRANSPLANTATION; and ARTIFICIAL ORGANS and BIOARTIFICIAL ORGANS and tissues.Homeodomain Proteins: Proteins encoded by homeobox genes (GENES, HOMEOBOX) that exhibit structural similarity to certain prokaryotic and eukaryotic DNA-binding proteins. Homeodomain proteins are involved in the control of gene expression during morphogenesis and development (GENE EXPRESSION REGULATION, DEVELOPMENTAL).Receptor, Notch1: A notch receptor that interacts with a variety of ligands and regulates SIGNAL TRANSDUCTION PATHWAYS for multiple cellular processes. It is widely expressed during EMBRYOGENESIS and is essential for EMBRYONIC DEVELOPMENT.Brain Tissue Transplantation: Transference of brain tissue, either from a fetus or from a born individual, between individuals of the same species or between individuals of different species.Nerve Regeneration: Renewal or physiological repair of damaged nerve tissue.Biological Markers: Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.Cell Transplantation: Transference of cells within an individual, between individuals of the same species, or between individuals of different species.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Fibroblast Growth Factor 2: A single-chain polypeptide growth factor that plays a significant role in the process of WOUND HEALING and is a potent inducer of PHYSIOLOGIC ANGIOGENESIS. Several different forms of the human protein exist ranging from 18-24 kDa in size due to the use of alternative start sites within the fgf-2 gene. It has a 55 percent amino acid residue identity to FIBROBLAST GROWTH FACTOR 1 and has potent heparin-binding activity. The growth factor is an extremely potent inducer of DNA synthesis in a variety of cell types from mesoderm and neuroectoderm lineages. It was originally named basic fibroblast growth factor based upon its chemical properties and to distinguish it from acidic fibroblast growth factor (FIBROBLAST GROWTH FACTOR 1).Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Bone Marrow Cells: Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells.Lentivirus: A genus of the family RETROVIRIDAE consisting of non-oncogenic retroviruses that produce multi-organ diseases characterized by long incubation periods and persistent infection. Lentiviruses are unique in that they contain open reading frames (ORFs) between the pol and env genes and in the 3' env region. Five serogroups are recognized, reflecting the mammalian hosts with which they are associated. HIV-1 is the type species.Hematopoietic Stem Cell Mobilization: The release of stem cells from the bone marrow into the peripheral blood circulation for the purpose of leukapheresis, prior to stem cell transplantation. Hematopoietic growth factors or chemotherapeutic agents often are used to stimulate the mobilization.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Antigens, CD15: A trisaccharide antigen expressed on glycolipids and many cell-surface glycoproteins. In the blood the antigen is found on the surface of NEUTROPHILS; EOSINOPHILS; and MONOCYTES. In addition, CD15 antigen is a stage-specific embryonic antigen.Nuclear Reprogramming: The process that reverts CELL NUCLEI of fully differentiated somatic cells to a pluripotent or totipotent state. This process can be achieved to a certain extent by NUCLEAR TRANSFER TECHNIQUES, such as fusing somatic cell nuclei with enucleated pluripotent embryonic stem cells or enucleated totipotent oocytes. GENE EXPRESSION PROFILING of the fused hybrid cells is used to determine the degree of reprogramming. Dramatic results of nuclear reprogramming include the generation of cloned mammals, such as Dolly the sheep in 1997.Neural Tube: A tube of ectodermal tissue in an embryo that will give rise to the CENTRAL NERVOUS SYSTEM, including the SPINAL CORD and the BRAIN. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. For malformation of the neural tube, see NEURAL TUBE DEFECTS.Hippocampus: A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.Gene Expression Profiling: The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.Coculture Techniques: A technique of culturing mixed cell types in vitro to allow their synergistic or antagonistic interactions, such as on CELL DIFFERENTIATION or APOPTOSIS. Coculture can be of different types of cells, tissues, or organs from normal or disease states.HMGB Proteins: A family of sequence-related proteins similar to HMGB1 PROTEIN that contains specific HMG-BOX DOMAINS.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Polycomb Repressive Complex 1: A multisubunit polycomb protein complex with affinity for CHROMATIN that contains methylated HISTONE H3. It contains an E3 ubiquitin ligase activity that is specific for HISTONE H2A and works in conjunction with POLYCOMB REPRESSIVE COMPLEX 2 to effect EPIGENETIC REPRESSION.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Glioma: Benign and malignant central nervous system neoplasms derived from glial cells (i.e., astrocytes, oligodendrocytes, and ependymocytes). Astrocytes may give rise to astrocytomas (ASTROCYTOMA) or glioblastoma multiforme (see GLIOBLASTOMA). Oligodendrocytes give rise to oligodendrogliomas (OLIGODENDROGLIOMA) and ependymocytes may undergo transformation to become EPENDYMOMA; CHOROID PLEXUS NEOPLASMS; or colloid cysts of the third ventricle. (From Escourolle et al., Manual of Basic Neuropathology, 2nd ed, p21)Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Cell- and Tissue-Based Therapy: Therapies that involve the TRANSPLANTATION of CELLS or TISSUES developed for the purpose of restoring the function of diseased or dysfunctional cells or tissues.Glioblastoma: A malignant form of astrocytoma histologically characterized by pleomorphism of cells, nuclear atypia, microhemorrhage, and necrosis. They may arise in any region of the central nervous system, with a predilection for the cerebral hemispheres, basal ganglia, and commissural pathways. Clinical presentation most frequently occurs in the fifth or sixth decade of life with focal neurologic signs or seizures.Animals, Newborn: Refers to animals in the period of time just after birth.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Cell Dedifferentiation: A reverse developmental process in which terminally differentiated cells with specialized functions revert back to a less differentiated stage within their own CELL LINEAGE.Repressor Proteins: Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Mice, SCID: Mice homozygous for the mutant autosomal recessive gene "scid" which is located on the centromeric end of chromosome 16. These mice lack mature, functional lymphocytes and are thus highly susceptible to lethal opportunistic infections if not chronically treated with antibiotics. The lack of B- and T-cell immunity resembles severe combined immunodeficiency (SCID) syndrome in human infants. SCID mice are useful as animal models since they are receptive to implantation of a human immune system producing SCID-human (SCID-hu) hematochimeric mice.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Epigenesis, Genetic: A genetic process by which the adult organism is realized via mechanisms that lead to the restriction in the possible fates of cells, eventually leading to their differentiated state. Mechanisms involved cause heritable changes to cells without changes to DNA sequence such as DNA METHYLATION; HISTONE modification; DNA REPLICATION TIMING; NUCLEOSOME positioning; and heterochromatization which result in selective gene expression or repression.Colony-Forming Units Assay: A cytologic technique for measuring the functional capacity of stem cells by assaying their activity.Transplantation, Heterologous: Transplantation between animals of different species.Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.Leukemia Inhibitory Factor: An INTERLEUKIN-6 related cytokine that exhibits pleiotrophic effects on many physiological systems that involve cell proliferation, differentiation, and survival. Leukemia inhibitory factor binds to and acts through the lif receptor.Ferrosoferric Oxide: Iron (II,III) oxide (Fe3O4). It is a black ore of IRON that forms opaque crystals and exerts strong magnetism.Spinal Cord Injuries: Penetrating and non-penetrating injuries to the spinal cord resulting from traumatic external forces (e.g., WOUNDS, GUNSHOT; WHIPLASH INJURIES; etc.).Culture Media, Conditioned: Culture media containing biologically active components obtained from previously cultured cells or tissues that have released into the media substances affecting certain cell functions (e.g., growth, lysis).Transplantation, Autologous: Transplantation of an individual's own tissue from one site to another site.Hematopoiesis: The development and formation of various types of BLOOD CELLS. Hematopoiesis can take place in the BONE MARROW (medullary) or outside the bone marrow (HEMATOPOIESIS, EXTRAMEDULLARY).Neoplasms, Nerve Tissue: Neoplasms composed of nerve tissue. This concept does not refer to neoplasms located in the nervous system or its component nerves.Transduction, Genetic: The transfer of bacterial DNA by phages from an infected bacterium to another bacterium. This also refers to the transfer of genes into eukaryotic cells by viruses. This naturally occurring process is routinely employed as a GENE TRANSFER TECHNIQUE.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Peripheral Blood Stem Cell Transplantation: Transplantation of stem cells collected from the peripheral blood. It is a less invasive alternative to direct marrow harvesting of hematopoietic stem cells. Enrichment of stem cells in peripheral blood can be achieved by inducing mobilization of stem cells from the BONE MARROW.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Antigens, CD: Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Tissue Scaffolds: Cell growth support structures composed of BIOCOMPATIBLE MATERIALS. They are specially designed solid support matrices for cell attachment in TISSUE ENGINEERING and GUIDED TISSUE REGENERATION uses.Wnt Proteins: Wnt proteins are a large family of secreted glycoproteins that play essential roles in EMBRYONIC AND FETAL DEVELOPMENT, and tissue maintenance. They bind to FRIZZLED RECEPTORS and act as PARACRINE PROTEIN FACTORS to initiate a variety of SIGNAL TRANSDUCTION PATHWAYS. The canonical Wnt signaling pathway stabilizes the transcriptional coactivator BETA CATENIN.Antigens, CD34: Glycoproteins found on immature hematopoietic cells and endothelial cells. They are the only molecules to date whose expression within the blood system is restricted to a small number of progenitor cells in the bone marrow.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Transplantation, Homologous: Transplantation between individuals of the same species. Usually refers to genetically disparate individuals in contradistinction to isogeneic transplantation for genetically identical individuals.Cell Shape: The quality of surface form or outline of CELLS.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Epidermal Growth Factor: A 6-kDa polypeptide growth factor initially discovered in mouse submaxillary glands. Human epidermal growth factor was originally isolated from urine based on its ability to inhibit gastric secretion and called urogastrone. Epidermal growth factor exerts a wide variety of biological effects including the promotion of proliferation and differentiation of mesenchymal and EPITHELIAL CELLS. It is synthesized as a transmembrane protein which can be cleaved to release a soluble active form.Clone Cells: A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed)MicroRNAs: Small double-stranded, non-protein coding RNAs, 21-25 nucleotides in length generated from single-stranded microRNA gene transcripts by the same RIBONUCLEASE III, Dicer, that produces small interfering RNAs (RNA, SMALL INTERFERING). They become part of the RNA-INDUCED SILENCING COMPLEX and repress the translation (TRANSLATION, GENETIC) of target RNA by binding to homologous 3'UTR region as an imperfect match. The small temporal RNAs (stRNAs), let-7 and lin-4, from C. elegans, are the first 2 miRNAs discovered, and are from a class of miRNAs involved in developmental timing.Rats, Nude: A mutant strain of Rattus norvegicus without a thymus and with depressed or absent T-cell function. This strain of rats may have a small amount of hair at times, but then lose it.Hedgehog Proteins: A family of intercellular signaling proteins that play and important role in regulating the development of many TISSUES and organs. Their name derives from the observation of a hedgehog-like appearance in DROSOPHILA embryos with genetic mutations that block their action.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Fetal Blood: Blood of the fetus. Exchange of nutrients and waste between the fetal and maternal blood occurs via the PLACENTA. The cord blood is blood contained in the umbilical vessels (UMBILICAL CORD) at the time of delivery.Bone Morphogenetic Protein 4: A bone morphogenetic protein that is a potent inducer of bone formation. It also functions as a regulator of MESODERM formation during EMBRYONIC DEVELOPMENT.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Recovery of Function: A partial or complete return to the normal or proper physiologic activity of an organ or part following disease or trauma.Spinal Cord: A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.Oligonucleotide Array Sequence Analysis: Hybridization of a nucleic acid sample to a very large set of OLIGONUCLEOTIDE PROBES, which have been attached individually in columns and rows to a solid support, to determine a BASE SEQUENCE, or to detect variations in a gene sequence, GENE EXPRESSION, or for GENE MAPPING.Electroporation: A technique in which electric pulses of intensity in kilovolts per centimeter and of microsecond-to-millisecond duration cause a temporary loss of the semipermeability of CELL MEMBRANES, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA.Genetic Vectors: DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Neurodegenerative Diseases: Hereditary and sporadic conditions which are characterized by progressive nervous system dysfunction. These disorders are often associated with atrophy of the affected central or peripheral nervous system structures.Magnetite Nanoparticles: Synthesized magnetic particles under 100 nanometers possessing many biomedical applications including DRUG DELIVERY SYSTEMS and CONTRAST AGENTS. The particles are usually coated with a variety of polymeric compounds.Spermatogonia: Euploid male germ cells of an early stage of SPERMATOGENESIS, derived from prespermatogonia. With the onset of puberty, spermatogonia at the basement membrane of the seminiferous tubule proliferate by mitotic then meiotic divisions and give rise to the haploid SPERMATOCYTES.Real-Time Polymerase Chain Reaction: Methods used for detecting the amplified DNA products from the polymerase chain reaction as they accumulate instead of at the end of the reaction.Retroviridae: Family of RNA viruses that infects birds and mammals and encodes the enzyme reverse transcriptase. The family contains seven genera: DELTARETROVIRUS; LENTIVIRUS; RETROVIRUSES TYPE B, MAMMALIAN; ALPHARETROVIRUS; GAMMARETROVIRUS; RETROVIRUSES TYPE D; and SPUMAVIRUS. A key feature of retrovirus biology is the synthesis of a DNA copy of the genome which is integrated into cellular DNA. After integration it is sometimes not expressed but maintained in a latent state (PROVIRUSES).Mesencephalon: The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the PONS and the DIENCEPHALON. Midbrain contains two major parts, the dorsal TECTUM MESENCEPHALI and the ventral TEGMENTUM MESENCEPHALI, housing components of auditory, visual, and other sensorimoter systems.RNA, Small Interfering: Small double-stranded, non-protein coding RNAs (21-31 nucleotides) involved in GENE SILENCING functions, especially RNA INTERFERENCE (RNAi). Endogenously, siRNAs are generated from dsRNAs (RNA, DOUBLE-STRANDED) by the same ribonuclease, Dicer, that generates miRNAs (MICRORNAS). The perfect match of the siRNAs' antisense strand to their target RNAs mediates RNAi by siRNA-guided RNA cleavage. siRNAs fall into different classes including trans-acting siRNA (tasiRNA), repeat-associated RNA (rasiRNA), small-scan RNA (scnRNA), and Piwi protein-interacting RNA (piRNA) and have different specific gene silencing functions.Culture Media, Serum-Free: CULTURE MEDIA free of serum proteins but including the minimal essential substances required for cell growth. This type of medium avoids the presence of extraneous substances that may affect cell proliferation or unwanted activation of cells.Graft Survival: The survival of a graft in a host, the factors responsible for the survival and the changes occurring within the graft during growth in the host.Cell Transformation, Neoplastic: Cell changes manifested by escape from control mechanisms, increased growth potential, alterations in the cell surface, karyotypic abnormalities, morphological and biochemical deviations from the norm, and other attributes conferring the ability to invade, metastasize, and kill.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Cell Aging: The decrease in the cell's ability to proliferate with the passing of time. Each cell is programmed for a certain number of cell divisions and at the end of that time proliferation halts. The cell enters a quiescent state after which it experiences CELL DEATH via the process of APOPTOSIS.Rats, Transgenic: Laboratory rats that have been produced from a genetically manipulated rat EGG or rat EMBRYO, MAMMALIAN. They contain genes from another species.Microscopy, Confocal: A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.Nuclear Receptor Subfamily 6, Group A, Member 1: An orphan nuclear receptor expressed mainly in the GERM CELLS of GONADS. It functions as a transcription factor that binds to a direct repeat of the sequence AGGTCA and may play a role in the regulation of EMBRYOGENESIS and germ cell differentiation.Wnt Signaling Pathway: A complex signaling pathway whose name is derived from the DROSOPHILA Wg gene, which when mutated results in the wingless phenotype, and the vertebrate INT gene, which is located near integration sites of MOUSE MAMMARY TUMOR VIRUS. The signaling pathway is initiated by the binding of WNT PROTEINS to cells surface WNT RECEPTORS which interact with the AXIN SIGNALING COMPLEX and an array of second messengers that influence the actions of BETA CATENIN.Drosophila Proteins: Proteins that originate from insect species belonging to the genus DROSOPHILA. The proteins from the most intensely studied species of Drosophila, DROSOPHILA MELANOGASTER, are the subject of much interest in the area of MORPHOGENESIS and development.Tissue Engineering: Generating tissue in vitro for clinical applications, such as replacing wounded tissues or impaired organs. The use of TISSUE SCAFFOLDING enables the generation of complex multi-layered tissues and tissue structures.Cell Communication: Any of several ways in which living cells of an organism communicate with one another, whether by direct contact between cells or by means of chemical signals carried by neurotransmitter substances, hormones, and cyclic AMP.Chimera: An individual that contains cell populations derived from different zygotes.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Bone Morphogenetic Proteins: Bone-growth regulatory factors that are members of the transforming growth factor-beta superfamily of proteins. They are synthesized as large precursor molecules which are cleaved by proteolytic enzymes. The active form can consist of a dimer of two identical proteins or a heterodimer of two related bone morphogenetic proteins.Cell Transdifferentiation: A naturally occurring phenomenon where terminally differentiated cells dedifferentiate to the point where they can switch CELL LINEAGES. The cells then differentiate into other cell types.Janus Kinases: A family of intracellular tyrosine kinases that participate in the signaling cascade of cytokines by associating with specific CYTOKINE RECEPTORS. They act upon STAT TRANSCRIPTION FACTORS in signaling pathway referred to as the JAK/STAT pathway. The name Janus kinase refers to the fact the proteins have two phosphate-transferring domains.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Cell Line, Tumor: A cell line derived from cultured tumor cells.Tubulin: A microtubule subunit protein found in large quantities in mammalian brain. It has also been isolated from SPERM FLAGELLUM; CILIA; and other sources. Structurally, the protein is a dimer with a molecular weight of approximately 120,000 and a sedimentation coefficient of 5.8S. It binds to COLCHICINE; VINCRISTINE; and VINBLASTINE.Asymmetric Cell Division: Unequal cell division that results in daughter cells of different sizes.Proto-Oncogene Proteins c-kit: A protein-tyrosine kinase receptor that is specific for STEM CELL FACTOR. This interaction is crucial for the development of hematopoietic, gonadal, and pigment stem cells. Genetic mutations that disrupt the expression of PROTO-ONCOGENE PROTEINS C-KIT are associated with PIEBALDISM, while overexpression or constitutive activation of the c-kit protein-tyrosine kinase is associated with tumorigenesis.Primary Cell Culture: The initial culturing of cells derived directly from fresh TISSUES.Medulloblastoma: A malignant neoplasm that may be classified either as a glioma or as a primitive neuroectodermal tumor of childhood (see NEUROECTODERMAL TUMOR, PRIMITIVE). The tumor occurs most frequently in the first decade of life with the most typical location being the cerebellar vermis. Histologic features include a high degree of cellularity, frequent mitotic figures, and a tendency for the cells to organize into sheets or form rosettes. Medulloblastoma have a high propensity to spread throughout the craniospinal intradural axis. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2060-1)Cord Blood Stem Cell Transplantation: Transplantation of STEM CELLS collected from the fetal blood remaining in the UMBILICAL CORD and the PLACENTA after delivery. Included are the HEMATOPOIETIC STEM CELLS.Deoxyuridine: 2'-Deoxyuridine. An antimetabolite that is converted to deoxyuridine triphosphate during DNA synthesis. Laboratory suppression of deoxyuridine is used to diagnose megaloblastic anemias due to vitamin B12 and folate deficiencies.Peptides: Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.Kruppel-Like Transcription Factors: A family of zinc finger transcription factors that share homology with Kruppel protein, Drosophila. They contain a highly conserved seven amino acid spacer sequence in between their ZINC FINGER MOTIFS.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Cell Growth Processes: Processes required for CELL ENLARGEMENT and CELL PROLIFERATION.Nerve Tissue: Differentiated tissue of the central nervous system composed of NERVE CELLS, fibers, DENDRITES, and specialized supporting cells.Macrocephaly: A congenital abnormality in which the occipitofrontal circumference is greater than two standard deviations above the mean for a given age. It is associated with HYDROCEPHALUS; SUBDURAL EFFUSION; ARACHNOID CYSTS; or is part of a genetic condition (e.g., ALEXANDER DISEASE; SOTOS SYNDROME).In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Mice, Inbred NOD: A strain of non-obese diabetic mice developed in Japan that has been widely studied as a model for T-cell-dependent autoimmune insulin-dependent diabetes mellitus in which insulitis is a major histopathologic feature, and in which genetic susceptibility is strongly MHC-linked.Mice, Mutant Strains: Mice bearing mutant genes which are phenotypically expressed in the animals.Luminescent Proteins: Proteins which are involved in the phenomenon of light emission in living systems. Included are the "enzymatic" and "non-enzymatic" types of system with or without the presence of oxygen or co-factors.Teratogenesis: The formation of CONGENITAL ABNORMALITIES.RNA Interference: A gene silencing phenomenon whereby specific dsRNAs (RNA, DOUBLE-STRANDED) trigger the degradation of homologous mRNA (RNA, MESSENGER). The specific dsRNAs are processed into SMALL INTERFERING RNA (siRNA) which serves as a guide for cleavage of the homologous mRNA in the RNA-INDUCED SILENCING COMPLEX. DNA METHYLATION may also be triggered during this process.Transgenes: Genes that are introduced into an organism using GENE TRANSFER TECHNIQUES.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Microarray Analysis: The simultaneous analysis, on a microchip, of multiple samples or targets arranged in an array format.Genetic Therapy: Techniques and strategies which include the use of coding sequences and other conventional or radical means to transform or modify cells for the purpose of treating or reversing disease conditions.Embryonic Development: Morphological and physiological development of EMBRYOS.Intercellular Signaling Peptides and Proteins: Regulatory proteins and peptides that are signaling molecules involved in the process of PARACRINE COMMUNICATION. They are generally considered factors that are expressed by one cell and are responded to by receptors on another nearby cell. They are distinguished from HORMONES in that their actions are local rather than distal.Up-Regulation: A positive regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.Nerve Growth Factors: Factors which enhance the growth potentialities of sensory and sympathetic nerve cells.Germ Cells: The reproductive cells in multicellular organisms at various stages during GAMETOGENESIS.Chromatin Immunoprecipitation: A technique for identifying specific DNA sequences that are bound, in vivo, to proteins of interest. It involves formaldehyde fixation of CHROMATIN to crosslink the DNA-BINDING PROTEINS to the DNA. After shearing the DNA into small fragments, specific DNA-protein complexes are isolated by immunoprecipitation with protein-specific ANTIBODIES. Then, the DNA isolated from the complex can be identified by PCR amplification and sequencing.Hair Follicle: A tube-like invagination of the EPIDERMIS from which the hair shaft develops and into which SEBACEOUS GLANDS open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. (Stedman, 26th ed) Follicles of very long hairs extend into the subcutaneous layer of tissue under the SKIN.Cell Death: The termination of the cell's ability to carry out vital functions such as metabolism, growth, reproduction, responsiveness, and adaptability.Receptors, Cytoplasmic and Nuclear: Intracellular receptors that can be found in the cytoplasm or in the nucleus. They bind to extracellular signaling molecules that migrate through or are transported across the CELL MEMBRANE. Many members of this class of receptors occur in the cytoplasm and are transported to the CELL NUCLEUS upon ligand-binding where they signal via DNA-binding and transcription regulation. Also included in this category are receptors found on INTRACELLULAR MEMBRANES that act via mechanisms similar to CELL SURFACE RECEPTORS.beta Catenin: A multi-functional catenin that participates in CELL ADHESION and nuclear signaling. Beta catenin binds CADHERINS and helps link their cytoplasmic tails to the ACTIN in the CYTOSKELETON via ALPHA CATENIN. It also serves as a transcriptional co-activator and downstream component of WNT PROTEIN-mediated SIGNAL TRANSDUCTION PATHWAYS.Brain Stem: The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.