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)Tumor Cells, Cultured: Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.Cell Culture Techniques: Methods for maintaining or growing CELLS in vitro.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.Furylfuramide: Used formerly as antimicrobial food additive. It causes mutations in many cell cultures and may be carcinogenic.Cell Aggregation: The phenomenon by which dissociated cells intermixed in vitro tend to group themselves with cells of their own type.Neuroaxonal Dystrophies: A nonspecific term referring both to the pathologic finding of swelling of distal portions of axons in the brain and to disorders which feature this finding. Neuroaxonal dystrophy is seen in various genetic diseases, vitamin deficiencies, and aging. Infantile neuroaxonal dystrophy is an autosomal recessive disease characterized by arrested psychomotor development at 6 months to 2 years of age, ataxia, brain stem dysfunction, and quadriparesis. Juvenile and adult forms also occur. Pathologic findings include brain atrophy and widespread accumulation of axonal spheroids throughout the neuroaxis, peripheral nerves, and dental pulp. (From Davis & Robertson, Textbook of Neuropathology, 2nd ed, p927)Liver, Artificial: Devices for simulating the activities of the liver. They often consist of a hybrid between both biological and artificial materials.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)Actinium: Actinium. A trivalent radioactive element and the prototypical member of the actinide family. It has the atomic symbol Ac, atomic number 89, and atomic weight 227.0278. Its principal isotope is 227 and decays primarily by beta-emission.Misonidazole: A nitroimidazole that sensitizes normally radio-resistant hypoxic cells to radiation. It may also be directly cytotoxic to hypoxic cells and has been proposed as an antineoplastic.Cell Line, Tumor: A cell line derived from cultured tumor cells.Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Alpha Particles: Positively charged particles composed of two protons and two NEUTRONS, i.e. equivalent to HELIUM nuclei, which are emitted during disintegration of heavy ISOTOPES. Alpha rays have very strong ionizing power, but weak penetrability.Lomustine: An alkylating agent of value against both hematologic malignancies and solid tumors.Cytological Techniques: Methods used to study CELLS.Biodegradable Plastics: Organic polymeric materials which can be broken down by naturally occurring processes. This includes plastics created from bio-based or petrochemical-based materials.Leukoencephalopathies: Any of various diseases affecting the white matter of the central nervous system.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.Neoplastic Stem Cells: Highly proliferative, self-renewing, and colony-forming stem cells which give rise to NEOPLASMS.Mammary Neoplasms, Experimental: Experimentally induced mammary neoplasms in animals to provide a model for studying human BREAST NEOPLASMS.Organoids: An organization of cells into an organ-like structure. Organoids can be generated in culture. They are also found in certain neoplasms.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Neoplasms, Experimental: Experimentally induced new abnormal growth of TISSUES in animals to provide models for studying human neoplasms.Antineoplastic Agents: Substances that inhibit or prevent the proliferation of NEOPLASMS.NitroimidazolesProton Ionophores: Chemical agents that increase the permeability of CELL MEMBRANES to PROTONS.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.Peplomycin: An antineoplastic agent derived from BLEOMYCIN.Colonic Neoplasms: Tumors or cancer of the COLON.Neoplasm Transplantation: Experimental transplantation of neoplasms in laboratory animals for research purposes.Transplantation, Heterologous: Transplantation between animals of different species.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.Volvox: A genus of GREEN ALGAE in the family Volvocaceae. They form spherical colonies of hundreds or thousands of bi-flagellated cells in a semi-transparent gelatinous ball.Mechlorethamine: A biologic alkylating agent that exerts its cytotoxic effects by forming DNA ADDUCTS and DNA interstrand crosslinks, thereby inhibiting rapidly proliferating cells. The hydrochloride is an antineoplastic agent used to treat HODGKIN DISEASE and LYMPHOMA.Cell SeparationCell Adhesion: Adherence of cells to surfaces or to other cells.Dose-Response Relationship, Radiation: The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation.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 Movement: The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.Hepatocytes: The main structural component of the LIVER. They are specialized EPITHELIAL CELLS that are organized into interconnected plates called lobules.Hematoporphyrin Photoradiation: Photochemotherapy using visible light, usually red, topically or delivered locally by fiberoptic probe to tissues sensitized with hematoporphyrins.Diffusion: The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially FACILITATED DIFFUSION, is a major mechanism of BIOLOGICAL TRANSPORT.Cystadenocarcinoma: A malignant neoplasm derived from glandular epithelium, in which cystic accumulations of retained secretions are formed. The neoplastic cells manifest varying degrees of anaplasia and invasiveness, and local extension and metastases occur. Cystadenocarcinomas develop frequently in the ovaries, where pseudomucinous and serous types are recognized. (Stedman, 25th ed)Enzyme Multiplied Immunoassay Technique: An immunoenzyme test for the presence of drugs and other substances in urine and blood. The test uses enzyme linked antibodies that react only with the particular drug for which the sample is being tested.Cellular Microenvironment: Local surroundings with which cells interact by processing various chemical and physical signals, and by contributing their own effects to this environment.Tumor Stem Cell Assay: A cytologic technique for measuring the functional capacity of tumor stem cells by assaying their activity. It is used primarily for the in vitro testing of antineoplastic agents.Neoplasm Invasiveness: Ability of neoplasms to infiltrate and actively destroy surrounding tissue.Astatine: Astatine. A radioactive halogen with the atomic symbol At, atomic number 85, and atomic weight 210. Its isotopes range in mass number from 200 to 219 and all have an extremely short half-life. Astatine may be of use in the treatment of hyperthyroidism.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.Doxorubicin: Antineoplastic antibiotic obtained from Streptomyces peucetius. It is a hydroxy derivative of DAUNORUBICIN.Radiation Tolerance: The ability of some cells or tissues to survive lethal doses of IONIZING RADIATION. Tolerance depends on the species, cell type, and physical and chemical variables, including RADIATION-PROTECTIVE AGENTS and RADIATION-SENSITIZING AGENTS.Drug Resistance, Neoplasm: Resistance or diminished response of a neoplasm to an antineoplastic agent in humans, animals, or cell or tissue cultures.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 Hypoxia: A condition of decreased oxygen content at the cellular level.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.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Mitochondrial Degradation: Proteolytic breakdown of the MITOCHONDRIA.Cricetulus: A genus of the family Muridae consisting of eleven species. C. migratorius, the grey or Armenian hamster, and C. griseus, the Chinese hamster, are the two species used in biomedical research.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.Mice, Nude: Mutant mice homozygous for the recessive gene "nude" which fail to develop a thymus. They are useful in tumor studies and studies on immune responses.Tumor Microenvironment: The milieu surrounding neoplasms consisting of cells, vessels, soluble factors, and molecules, that can influence and be influenced by, the neoplasm's growth.Polyhydroxyethyl Methacrylate: A biocompatible, hydrophilic, inert gel that is permeable to tissue fluids. It is used as an embedding medium for microscopy, as a coating for implants and prostheses, for contact lenses, as microspheres in adsorption research, etc.Melanoma: A malignant neoplasm derived from cells that are capable of forming melanin, which may occur in the skin of any part of the body, in the eye, or, rarely, in the mucous membranes of the genitalia, anus, oral cavity, or other sites. It occurs mostly in adults and may originate de novo or from a pigmented nevus or malignant lentigo. Melanomas frequently metastasize widely, and the regional lymph nodes, liver, lungs, and brain are likely to be involved. The incidence of malignant skin melanomas is rising rapidly in all parts of the world. (Stedman, 25th ed; from Rook et al., Textbook of Dermatology, 4th ed, p2445)Radiation-Sensitizing Agents: Drugs used to potentiate the effectiveness of radiation therapy in destroying unwanted cells.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.Fibroblasts: Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Photochemotherapy: Therapy using oral or topical photosensitizing agents with subsequent exposure to light.Ovarian Neoplasms: Tumors or cancer of the OVARY. These neoplasms can be benign or malignant. They are classified according to the tissue of origin, such as the surface EPITHELIUM, the stromal endocrine cells, and the totipotent GERM CELLS.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.Iodine Radioisotopes: Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes.Cadherins: Calcium-dependent cell adhesion proteins. They are important in the formation of ADHERENS JUNCTIONS between cells. Cadherins are classified by their distinct immunological and tissue specificities, either by letters (E- for epithelial, N- for neural, and P- for placental cadherins) or by numbers (cadherin-12 or N-cadherin 2 for brain-cadherin). Cadherins promote cell adhesion via a homophilic mechanism as in the construction of tissues and of the whole animal body.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Necrosis: The pathological process occurring in cells that are dying from irreparable injuries. It is caused by the progressive, uncontrolled action of degradative ENZYMES, leading to MITOCHONDRIAL SWELLING, nuclear flocculation, and cell lysis. It is distinct it from APOPTOSIS, which is a normal, regulated cellular process.Drug Screening Assays, Antitumor: Methods of investigating the effectiveness of anticancer cytotoxic drugs and biologic inhibitors. These include in vitro cell-kill models and cytostatic dye exclusion tests as well as in vivo measurement of tumor growth parameters in laboratory animals.