Freeze Etching: A replica technique in which cells are frozen to a very low temperature and cracked with a knife blade to expose the interior surfaces of the cells or cell membranes. The cracked cell surfaces are then freeze-dried to expose their constituents. The surfaces are now ready for shadowing to be viewed using an electron microscope. This method differs from freeze-fracturing in that no cryoprotectant is used and, thus, allows for the sublimation of water during the freeze-drying process to etch the surfaces.Freeze Drying: Method of tissue preparation in which the tissue specimen is frozen and then dehydrated at low temperature in a high vacuum. This method is also used for dehydrating pharmaceutical and food products.Acid Etching, Dental: Preparation of TOOTH surfaces and DENTAL MATERIALS with etching agents, usually phosphoric acid, to roughen the surface to increase adhesion or osteointegration.Freeze Fracturing: Preparation for electron microscopy of minute replicas of exposed surfaces of the cell which have been ruptured in the frozen state. The specimen is frozen, then cleaved under high vacuum at the same temperature. The exposed surface is shadowed with carbon and platinum and coated with carbon to obtain a carbon replica.Dental Etching: Preparation of TOOTH surfaces, and of materials bonded to teeth or DENTAL IMPLANTS, with agents and methods which roughen the surface to facilitate adhesion. Agents include phosphoric or other acids (ACID ETCHING, DENTAL) and methods include LASERS.Freeze Substitution: A modification of the freeze-drying method in which the ice within the frozen tissue is replaced by alcohol or other solvent at a very low temperature.Freezing: Liquids transforming into solids by the removal of heat.Erythrocyte Membrane: The semi-permeable outer structure of a red blood cell. It is known as a red cell 'ghost' after HEMOLYSIS.Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Tetrathionic Acid: A sulfuric acid dimer, formed by disulfide linkage. This compound has been used to prolong coagulation time and as an antidote in cyanide poisoning.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Intracellular Membranes: Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Paramecium: A genus of ciliate protozoa that is often large enough to be seen by the naked eye. Paramecia are commonly used in genetic, cytological, and other research.Mitochondrial Membranes: The two lipoprotein layers in the MITOCHONDRION. The outer membrane encloses the entire mitochondrion and contains channels with TRANSPORT PROTEINS to move molecules and ions in and out of the organelle. The inner membrane folds into cristae and contains many ENZYMES important to cell METABOLISM and energy production (MITOCHONDRIAL ATP SYNTHASE).Mitochondria: Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)Subfornical Organ: A structure, situated close to the intraventricular foramen, which induces DRINKING BEHAVIOR after stimulation with ANGIOTENSIN II.Synaptic Vesicles: Membrane-bound compartments which contain transmitter molecules. Synaptic vesicles are concentrated at presynaptic terminals. They actively sequester transmitter molecules from the cytoplasm. In at least some synapses, transmitter release occurs by fusion of these vesicles with the presynaptic membrane, followed by exocytosis of their contents.Pinocytosis: The engulfing of liquids by cells by a process of invagination and closure of the cell membrane to form fluid-filled vacuoles.Stapedius: A tiny muscle that arises from the posterior wall of the TYMPANIC CAVITY of MIDDLE EAR with its tendon inserted onto the neck of the STAPES. Stapedius pulls the stapes posteriorly and controls its movement.Staining and Labeling: The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.Tobacco: A plant genus of the family SOLANACEAE. Members contain NICOTINE and other biologically active chemicals; its dried leaves are used for SMOKING.Plants, Toxic: Plants or plant parts which are harmful to man or other animals.Plants, Genetically Modified: PLANTS, or their progeny, whose GENOME has been altered by GENETIC ENGINEERING.Tobacco Mosaic Virus: The type species of TOBAMOVIRUS which causes mosaic disease of tobacco. Transmission occurs by mechanical inoculation.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Arabidopsis: A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.Libraries, Digital: Libraries in which a major proportion of the resources are available in machine-readable format, rather than on paper or MICROFORM.Libraries: Collections of systematically acquired and organized information resources, and usually providing assistance to users. (ERIC Thesaurus, accessed 2/1/2008)Library Automation: The use of automatic machines or processing devices in libraries. The automation may be applied to library administrative activities, office procedures, and delivery of library services to users.Library Collection Development: Development of a library collection, including the determination and coordination of selection policy, assessment of needs of users and potential users, collection use studies, collection evaluation, identification of collection needs, selection of materials, planning for resource sharing, collection maintenance and weeding, and budgeting.Libraries, MedicalInformation Storage and Retrieval: Organized activities related to the storage, location, search, and retrieval of information.Search Engine: Software used to locate data or information stored in machine-readable form locally or at a distance such as an INTERNET site.Commerce: The interchange of goods or commodities, especially on a large scale, between different countries or between populations within the same country. It includes trade (the buying, selling, or exchanging of commodities, whether wholesale or retail) and business (the purchase and sale of goods to make a profit). (From Random House Unabridged Dictionary, 2d ed, p411, p2005 & p283)Taxes: Governmental levies on property, inheritance, gifts, etc.Prescription Fees: The charge levied on the consumer for drugs or therapy prescribed under written order of a physician or other health professional.Philately: Study of stamps or postal markings. It usually refers to the design and commemorative aspects of the stamp.Great BritainGermanyMedicine, Arabic: Traditional Arabic methods used in medicine in the ARAB WORLD.Engraving and EngravingsAviation: Design, development, manufacture, and operation of heavier-than-air AIRCRAFT.United States National Aeronautics and Space Administration: An independent Federal agency established in 1958. It conducts research for the solution of problems of flight within and outside the Earth's atmosphere and develops, constructs, tests, and operates aeronautical and space vehicles. (From U.S. Government Manual, 1993)Accidents, AviationAerospace Medicine: That branch of medicine dealing with the studies and effects of flight through the atmosphere or in space upon the human body and with the prevention or cure of physiological or psychological malfunctions arising from these effects. (from NASA Thesaurus)Inventors: Persons or entities that introduce a novel composition, device, or process, as well as improvements thereof.ParisElectron Transport: The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270)Hepatitis, Infectious Canine: A contagious disease caused by canine adenovirus (ADENOVIRUSES, CANINE) infecting the LIVER, the EYE, the KIDNEY, and other organs in dogs, other canids, and bears. Symptoms include FEVER; EDEMA; VOMITING; and DIARRHEA.Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Nursing Informatics: The field of information science concerned with the analysis and dissemination of data through the application of computers applied to the field of nursing.Dog Diseases: Diseases of the domestic dog (Canis familiaris). This term does not include diseases of wild dogs, WOLVES; FOXES; and other Canidae for which the heading CARNIVORA is used.