Permeability: Property of membranes and other structures to permit passage of light, heat, gases, liquids, metabolites, and mineral ions.Cell Membrane Permeability: A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.Capillary Permeability: The property of blood capillary ENDOTHELIUM that allows for the selective exchange of substances between the blood and surrounding tissues and through membranous barriers such as the BLOOD-AIR BARRIER; BLOOD-AQUEOUS BARRIER; BLOOD-BRAIN BARRIER; BLOOD-NERVE BARRIER; BLOOD-RETINAL BARRIER; and BLOOD-TESTIS BARRIER. Small lipid-soluble molecules such as carbon dioxide and oxygen move freely by diffusion. Water and water-soluble molecules cannot pass through the endothelial walls and are dependent on microscopic pores. These pores show narrow areas (TIGHT JUNCTIONS) which may limit large molecule movement.Tight Junctions: Cell-cell junctions that seal adjacent epithelial cells together, preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other. (Alberts et al., Molecular Biology of the Cell, 2nd ed, p22)Blood-Brain Barrier: Specialized non-fenestrated tightly-joined ENDOTHELIAL CELLS with TIGHT JUNCTIONS that form a transport barrier for certain substances between the cerebral capillaries and the BRAIN tissue.Lactulose: A synthetic disaccharide used in the treatment of constipation and hepatic encephalopathy. It has also been used in the diagnosis of gastrointestinal disorders. (From Martindale, The Extra Pharmacopoeia, 30th ed, p887)Mannitol: A diuretic and renal diagnostic aid related to sorbitol. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity.Mitochondrial Membrane Transport Proteins: Proteins involved in the transport of specific substances across the membranes of the MITOCHONDRIA.Dentin Permeability: The property of dentin that permits passage of light, heat, cold, and chemical substances. It does not include penetration by microorganisms.Evans Blue: An azo dye used in blood volume and cardiac output measurement by the dye dilution method. It is very soluble, strongly bound to plasma albumin, and disappears very slowly.Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Occludin: A MARVEL domain protein that plays an important role in the formation and regulation of the TIGHT JUNCTION paracellular permeability barrier.Osmosis: Tendency of fluids (e.g., water) to move from the less concentrated to the more concentrated side of a semipermeable membrane.Intestinal Absorption: Uptake of substances through the lining of the INTESTINES.Aquaporins: A class of porins that allow the passage of WATER and other small molecules across CELL MEMBRANES.Mitochondrial Swelling: An increase in MITOCHONDRIAL VOLUME due to an influx of fluid; it occurs in hypotonic solutions due to osmotic pressure and in isotonic solutions as a result of altered permeability of the membranes of respiring mitochondria.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Biological Transport: The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.Electric Impedance: The resistance to the flow of either alternating or direct electrical current.Membrane Potentials: The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).Caco-2 Cells: Human colonic ADENOCARCINOMA cells that are able to express differentiation features characteristic of mature intestinal cells, such as ENTEROCYTES. These cells are valuable in vitro tools for studies related to intestinal cell function and differentiation.Aquaporin 1: Aquaporin 1 forms a water-specific channel that is constitutively expressed at the PLASMA MEMBRANE of ERYTHROCYTES and KIDNEY TUBULES, PROXIMAL. It provides these cells with a high permeability to WATER. In humans polymorphisms of this protein result in the Colton blood group antigen.Zonula Occludens-1 Protein: A 195-kDa zonula occludens protein that is distinguished by the presence of a ZU5 domain at the C-terminal of the molecule.Dextrans: A group of glucose polymers made by certain bacteria. Dextrans are used therapeutically as plasma volume expanders and anticoagulants. They are also commonly used in biological experimentation and in industry for a wide variety of purposes.Potassium: An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Blood-Retinal Barrier: A specialized transport barrier, in the EYE, formed by the retinal pigment EPITHELIUM, and the ENDOTHELIUM of the BLOOD VESSELS of the RETINA. TIGHT JUNCTIONS joining adjacent cells keep the barrier between cells continuous.Endothelium, Vascular: Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.Ion Channels: Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.Fluorescein: A phthalic indicator dye that appears yellow-green in normal tear film and bright green in a more alkaline medium such as the aqueous humor.Intercellular Junctions: Direct contact of a cell with a neighboring cell. Most such junctions are too small to be resolved by light microscopy, but they can be visualized by conventional or freeze-fracture electron microscopy, both of which show that the interacting CELL MEMBRANE and often the underlying CYTOPLASM and the intervening EXTRACELLULAR SPACE are highly specialized in these regions. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p792)Chlorides: Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.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.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.Albumins: Water-soluble proteins found in egg whites, blood, lymph, and other tissues and fluids. They coagulate upon heating.Cyclophilins: A family of peptidyl-prolyl cis-trans isomerases that bind to CYCLOSPORINS and regulate the IMMUNE SYSTEM. EC 5.2.1.-Intestinal Mucosa: Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI.Endothelial Cells: Highly specialized EPITHELIAL CELLS that line the HEART; BLOOD VESSELS; and lymph vessels, forming the ENDOTHELIUM. They are polygonal in shape and joined together by TIGHT JUNCTIONS. The tight junctions allow for variable permeability to specific macromolecules that are transported across the endothelial layer.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.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.Fluoresceins: A family of spiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one derivatives. These are used as dyes, as indicators for various metals, and as fluorescent labels in immunoassays.Inulin: A starch found in the tubers and roots of many plants. Since it is hydrolyzable to FRUCTOSE, it is classified as a fructosan. It has been used in physiologic investigation for determination of the rate of glomerular function.Claudins: A large family of transmembrane proteins found in TIGHT JUNCTIONS. They take part in the formation of paracellular barriers and pores that regulate paracellular permeability.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)Claudin-5: A claudin subtype that is found localized to TIGHT JUNCTIONS in VASCULAR ENDOTHELIAL CELLS. The protein was initially identified as one of several proteins which are deleted in VELOCARDIOFACIAL SYNDROME and may play an important role in maintaining the integrity of the BLOOD-BRAIN BARRIER.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Fluorescein-5-isothiocyanate: Fluorescent probe capable of being conjugated to tissue and proteins. It is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.Vascular Endothelial Growth Factor A: The original member of the family of endothelial cell growth factors referred to as VASCULAR ENDOTHELIAL GROWTH FACTORS. Vascular endothelial growth factor-A was originally isolated from tumor cells and referred to as "tumor angiogenesis factor" and "vascular permeability factor". Although expressed at high levels in certain tumor-derived cells it is produced by a wide variety of cell types. In addition to stimulating vascular growth and vascular permeability it may play a role in stimulating VASODILATION via NITRIC OXIDE-dependent pathways. Alternative splicing of the mRNA for vascular endothelial growth factor A results in several isoforms of the protein being produced.Blood-Air Barrier: The barrier between capillary blood and alveolar air comprising the alveolar EPITHELIUM and capillary ENDOTHELIUM with their adherent BASEMENT MEMBRANE and EPITHELIAL CELL cytoplasm. PULMONARY GAS EXCHANGE occurs across this membrane.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Skin Absorption: Uptake of substances through the SKIN.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.Mitochondria, Liver: Mitochondria in hepatocytes. As in all mitochondria, there are an outer membrane and an inner membrane, together creating two separate mitochondrial compartments: the internal matrix space and a much narrower intermembrane space. In the liver mitochondrion, an estimated 67% of the total mitochondrial proteins is located in the matrix. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p343-4)Pulmonary Edema: Excessive accumulation of extravascular fluid in the lung, an indication of a serious underlying disease or disorder. Pulmonary edema prevents efficient PULMONARY GAS EXCHANGE in the PULMONARY ALVEOLI, and can be life-threatening.Electric Conductivity: The ability of a substrate to allow the passage of ELECTRONS.Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.Membranes, Artificial: Artificially produced membranes, such as semipermeable membranes used in artificial kidney dialysis (RENAL DIALYSIS), monomolecular and bimolecular membranes used as models to simulate biological CELL MEMBRANES. These membranes are also used in the process of GUIDED TISSUE REGENERATION.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Cyclosporine: A cyclic undecapeptide from an extract of soil fungi. It is a powerful immunosupressant with a specific action on T-lymphocytes. It is used for the prophylaxis of graft rejection in organ and tissue transplantation. (From Martindale, The Extra Pharmacopoeia, 30th ed).Capillaries: The minute vessels that connect the arterioles and venules.Epithelium: One or more layers of EPITHELIAL CELLS, supported by the basal lamina, which covers the inner or outer surfaces of the body.Biological Transport, Active: The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.Osmolar Concentration: The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Tight Junction Proteins: Proteins that take part in the formation or structure of TIGHT JUNCTIONS.Urea: A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids.Diffusion Chambers, Culture: Devices used in a technique by which cells or tissues are grown in vitro or, by implantation, in vivo within chambers permeable to diffusion of solutes across the chamber walls. The chambers are used for studies of drug effects, osmotic responses, cytogenic and immunologic phenomena, metabolism, etc., and include tissue cages.Kinetics: The rate dynamics in chemical or physical systems.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Intestines: The section of the alimentary canal from the STOMACH to the ANAL CANAL. It includes the LARGE INTESTINE and SMALL INTESTINE.Body Water: Fluids composed mainly of water found within the body.Microcirculation: The circulation of the BLOOD through the MICROVASCULAR NETWORK.Fluorescent Dyes: Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.Vascular Endothelial Growth Factors: A family of angiogenic proteins that are closely-related to VASCULAR ENDOTHELIAL GROWTH FACTOR A. They play an important role in the growth and differentiation of vascular as well as lymphatic endothelial cells.Voltage-Dependent Anion Channels: A family of voltage-gated eukaryotic porins that form aqueous channels. They play an essential role in mitochondrial CELL MEMBRANE PERMEABILITY, are often regulated by BCL-2 PROTO-ONCOGENE PROTEINS, and have been implicated in APOPTOSIS.Rubidium: An element that is an alkali metal. It has an atomic symbol Rb, atomic number 37, and atomic weight 85.47. It is used as a chemical reagent and in the manufacture of photoelectric cells.Claudin-1: An integral membrane protein that is localized to TIGHT JUNCTIONS, where it plays a role in controlling the paracellular permeability of polarized cells. Mutations in the gene for claudin-1 are associated with Neonatal Ichthyosis-Sclerosing Cholangitis (NISCH) Syndrome.Bongkrekic Acid: An antibiotic produced by Pseudomonas cocovenenans. It is an inhibitor of MITOCHONDRIAL ADP, ATP TRANSLOCASES. Specifically, it blocks adenine nucleotide efflux from mitochondria by enhancing membrane binding.Venules: The minute vessels that collect blood from the capillary plexuses and join together to form veins.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.Endothelial Growth Factors: These growth factors are soluble mitogens secreted by a variety of organs. The factors are a mixture of two single chain polypeptides which have affinity to heparin. Their molecular weight are organ and species dependent. They have mitogenic and chemotactic effects and can stimulate endothelial cells to grow and synthesize DNA. The factors are related to both the basic and acidic FIBROBLAST GROWTH FACTORS but have different amino acid sequences.Histamine: An amine derived by enzymatic decarboxylation of HISTIDINE. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter.Lymphokines: Soluble protein factors generated by activated lymphocytes that affect other cells, primarily those involved in cellular immunity.Anions: Negatively charged atoms, radicals or groups of atoms which travel to the anode or positive pole during electrolysis.Edema: Abnormal fluid accumulation in TISSUES or body cavities. Most cases of edema are present under the SKIN in SUBCUTANEOUS TISSUE.Adherens Junctions: Anchoring points where the CYTOSKELETON of neighboring cells are connected to each other. They are composed of specialized areas of the plasma membrane where bundles of the ACTIN CYTOSKELETON attach to the membrane through the transmembrane linkers, CADHERINS, which in turn attach through their extracellular domains to cadherins in the neighboring cell membranes. In sheets of cells, they form into adhesion belts (zonula adherens) that go all the way around a cell.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Liposomes: Artificial, single or multilaminar vesicles (made from lecithins or other lipids) that are used for the delivery of a variety of biological molecules or molecular complexes to cells, for example, drug delivery and gene transfer. They are also used to study membranes and membrane proteins.Atractyloside: A glycoside of a kaurene type diterpene that is found in some plants including Atractylis gummifera (ATRACTYLIS); COFFEE; XANTHIUM, and CALLILEPIS. Toxicity is due to inhibition of ADENINE NUCLEOTIDE TRANSLOCASE.Skin: The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.Horseradish Peroxidase: An enzyme isolated from horseradish which is able to act as an antigen. It is frequently used as a histochemical tracer for light and electron microscopy. Its antigenicity has permitted its use as a combined antigen and marker in experimental immunology.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Rhamnose: A methylpentose whose L- isomer is found naturally in many plant glycosides and some gram-negative bacterial lipopolysaccharides.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Water-Electrolyte Balance: The balance of fluid in the BODY FLUID COMPARTMENTS; total BODY WATER; BLOOD VOLUME; EXTRACELLULAR SPACE; INTRACELLULAR SPACE, maintained by processes in the body that regulate the intake and excretion of WATER and ELECTROLYTES, particularly SODIUM and POTASSIUM.Anura: An order of the class Amphibia, which includes several families of frogs and toads. They are characterized by well developed hind limbs adapted for jumping, fused head and trunk and webbed toes. The term "toad" is ambiguous and is properly applied only to the family Bufonidae.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Fluorophotometry: Measurement of light given off by fluorescein in order to assess the integrity of various ocular barriers. The method is used to investigate the blood-aqueous barrier, blood-retinal barrier, aqueous flow measurements, corneal endothelial permeability, and tear flow dynamics.Cations: Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis.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, Heart: The mitochondria of the myocardium.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Serum Albumin, Radio-Iodinated: Normal human serum albumin mildly iodinated with radioactive iodine (131-I) which has a half-life of 8 days, and emits beta and gamma rays. It is used as a diagnostic aid in blood volume determination. (from Merck Index, 11th ed)Mice, Hairless: Mutant strains of mice that produce little or no hair.Chromium Radioisotopes: Unstable isotopes of chromium that decay or disintegrate emitting radiation. Cr atoms with atomic weights of 46-49, 51, 55, and 56 are radioactive chromium isotopes.Serum Albumin: A major protein in the BLOOD. It is important in maintaining the colloidal osmotic pressure and transporting large organic molecules.Mice, Inbred C57BLCadherins: 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.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.Potassium Isotopes: Stable potassium atoms that have the same atomic number as the element potassium, but differ in atomic weight. K-41 is a stable potassium isotope.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Aquaporin 3: Aquaporin 3 is an aquaglyceroporin that is expressed in the KIDNEY COLLECTING DUCTS and is constitutively localized at the basolateral MEMBRANE.Edetic Acid: A chelating agent that sequesters a variety of polyvalent cations such as CALCIUM. It is used in pharmaceutical manufacturing and as a food additive.Porins: Porins are protein molecules that were originally found in the outer membrane of GRAM-NEGATIVE BACTERIA and that form multi-meric channels for the passive DIFFUSION of WATER; IONS; or other small molecules. Porins are present in bacterial CELL WALLS, as well as in plant, fungal, mammalian and other vertebrate CELL MEMBRANES and MITOCHONDRIAL MEMBRANES.PhloretinColoring Agents: Chemicals and substances that impart color including soluble dyes and insoluble pigments. They are used in INKS; PAINTS; and as INDICATORS AND REAGENTS.Microvessels: The finer blood vessels of the vasculature that are generally less than 100 microns in internal diameter.Aquaporin 4: Aquaporin 4 is the major water-selective channel in the CENTRAL NERVOUS SYSTEM of mammals.Lipid Bilayers: Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes.Jejunum: The middle portion of the SMALL INTESTINE, between DUODENUM and ILEUM. It represents about 2/5 of the remaining portion of the small intestine below duodenum.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Osmotic Pressure: The pressure required to prevent the passage of solvent through a semipermeable membrane that separates a pure solvent from a solution of the solvent and solute or that separates different concentrations of a solution. It is proportional to the osmolality of the solution.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.Retinal Vessels: The blood vessels which supply and drain the RETINA.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.Endothelium: A layer of epithelium that lines the heart, blood vessels (ENDOTHELIUM, VASCULAR), lymph vessels (ENDOTHELIUM, LYMPHATIC), and the serous cavities of the body.Lanthanum: Lanthanum. The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.Membrane Potential, Mitochondrial: The voltage difference, normally maintained at approximately -180mV, across the INNER MITOCHONDRIAL MEMBRANE, by a net movement of positive charge across the membrane. It is a major component of the PROTON MOTIVE FORCE in MITOCHONDRIA used to drive the synthesis of ATP.Epidermis: The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).Ions: An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.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.Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Bradykinin: A nonapeptide messenger that is enzymatically produced from KALLIDIN in the blood where it is a potent but short-lived agent of arteriolar dilation and increased capillary permeability. Bradykinin is also released from MAST CELLS during asthma attacks, from gut walls as a gastrointestinal vasodilator, from damaged tissues as a pain signal, and may be a neurotransmitter.Gap Junctions: Connections between cells which allow passage of small molecules and electric current. Gap junctions were first described anatomically as regions of close apposition between cells with a narrow (1-2 nm) gap between cell membranes. The variety in the properties of gap junctions is reflected in the number of CONNEXINS, the family of proteins which form the junctions.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.Glycocalyx: The carbohydrate-rich zone on the cell surface. This zone can be visualized by a variety of stains as well as by its affinity for lectins. Although most of the carbohydrate is attached to intrinsic plasma membrane molecules, the glycocalyx usually also contains both glycoproteins and proteoglycans that have been secreted into the extracellular space and then adsorbed onto the cell surface. (Alberts et al., Molecular Biology of the Cell, 3d ed, p502)Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.Bacterial Translocation: The passage of viable bacteria from the GASTROINTESTINAL TRACT to extra-intestinal sites, such as the mesenteric lymph node complex, liver, spleen, kidney, and blood. Factors that promote bacterial translocation include overgrowth with gram-negative enteric bacilli, impaired host immune defenses, and injury to the INTESTINAL MUCOSA resulting in increased intestinal permeability. Bacterial translocation from the lung to the circulation is also possible and sometimes accompanies MECHANICAL VENTILATION.Vasopressins: Antidiuretic hormones released by the NEUROHYPOPHYSIS of all vertebrates (structure varies with species) to regulate water balance and OSMOLARITY. In general, vasopressin is a nonapeptide consisting of a six-amino-acid ring with a cysteine 1 to cysteine 6 disulfide bridge or an octapeptide containing a CYSTINE. All mammals have arginine vasopressin except the pig with a lysine at position 8. Vasopressin, a vasoconstrictor, acts on the KIDNEY COLLECTING DUCTS to increase water reabsorption, increase blood volume and blood pressure.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.Reactive Oxygen Species: Molecules or ions formed by the incomplete one-electron reduction of oxygen. These reactive oxygen intermediates include SINGLET OXYGEN; SUPEROXIDES; PEROXIDES; HYDROXYL RADICAL; and HYPOCHLOROUS ACID. They contribute to the microbicidal activity of PHAGOCYTES, regulation of signal transduction and gene expression, and the oxidative damage to NUCLEIC ACIDS; PROTEINS; and LIPIDS.Microscopy, Fluorescence: Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.Ouabain: A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.Technetium Tc 99m Pentetate: A technetium imaging agent used in renal scintigraphy, computed tomography, lung ventilation imaging, gastrointestinal scintigraphy, and many other procedures which employ radionuclide imaging agents.Kidney Tubules, Collecting: Straight tubes commencing in the radiate part of the kidney cortex where they receive the curved ends of the distal convoluted tubules. In the medulla the collecting tubules of each pyramid converge to join a central tube (duct of Bellini) which opens on the summit of the papilla.Intestine, Small: The portion of the GASTROINTESTINAL TRACT between the PYLORUS of the STOMACH and the ILEOCECAL VALVE of the LARGE INTESTINE. It is divisible into three portions: the DUODENUM, the JEJUNUM, and the ILEUM.Membranes: Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.Kidney Glomerulus: A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue.Ion Transport: The movement of ions across energy-transducing cell membranes. Transport can be active, passive or facilitated. Ions may travel by themselves (uniport), or as a group of two or more ions in the same (symport) or opposite (antiport) directions.Serum Albumin, Bovine: Serum albumin from cows, commonly used in in vitro biological studies. (From Stedman, 25th ed)Colon: The segment of LARGE INTESTINE between the CECUM and the RECTUM. It includes the ASCENDING COLON; the TRANSVERSE COLON; the DESCENDING COLON; and the SIGMOID COLON.Pulmonary Alveoli: Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place.Rats, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.Mitochondrial ADP, ATP Translocases: A class of nucleotide translocases found abundantly in mitochondria that function as integral components of the inner mitochondrial membrane. They facilitate the exchange of ADP and ATP between the cytosol and the mitochondria, thereby linking the subcellular compartments of ATP production to those of ATP utilization.Extravasation of Diagnostic and Therapeutic Materials: The escape of diagnostic or therapeutic material from the vessel into which it is introduced into the surrounding tissue or body cavity.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Blood-Aqueous Barrier: The selectively permeable barrier, in the EYE, formed by the nonpigmented layer of the EPITHELIUM of the CILIARY BODY, and the ENDOTHELIUM of the BLOOD VESSELS of the IRIS. TIGHT JUNCTIONS joining adjacent cells keep the barrier between cells continuous.Protons: Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.Cytochromes c: Cytochromes of the c type that are found in eukaryotic MITOCHONDRIA. They serve as redox intermediates that accept electrons from MITOCHONDRIAL ELECTRON TRANSPORT COMPLEX III and transfer them to MITOCHONDRIAL ELECTRON TRANSPORT COMPLEX IV.Tooth Permeability: The property of TEETH to permit passage of light, heat, gases, liquids, metabolites, mineral ions and other substances. It does not include the penetration of the teeth by microorganisms.Brain Edema: Increased intracellular or extracellular fluid in brain tissue. Cytotoxic brain edema (swelling due to increased intracellular fluid) is indicative of a disturbance in cell metabolism, and is commonly associated with hypoxic or ischemic injuries (see HYPOXIA, BRAIN). An increase in extracellular fluid may be caused by increased brain capillary permeability (vasogenic edema), an osmotic gradient, local blockages in interstitial fluid pathways, or by obstruction of CSF flow (e.g., obstructive HYDROCEPHALUS). (From Childs Nerv Syst 1992 Sep; 8(6):301-6)Erythritol: A four-carbon sugar that is found in algae, fungi, and lichens. It is twice as sweet as sucrose and can be used as a coronary vasodilator.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.Absorption: The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.Pulmonary Circulation: The circulation of the BLOOD through the LUNGS.Oocytes: Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).Mesentery: A layer of the peritoneum which attaches the abdominal viscera to the ABDOMINAL WALL and conveys their blood vessels and nerves.Extracellular Space: Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone: A proton ionophore that is commonly used as an uncoupling agent in biochemical studies.Claudin-4: A claudin subtype that takes part in maintaining the barrier-forming property of TIGHT JUNCTIONS. Claudin-4 is found associated with CLAUDIN-8 in the KIDNEY COLLECTING DUCT where it may play a role in paracellular chloride ion reabsorption.Rana pipiens: A highly variable species of the family Ranidae in Canada, the United States and Central America. It is the most widely used Anuran in biomedical research.Cations, Monovalent: Positively charged atoms, radicals or group of atoms with a valence of plus 1, which travel to the cathode or negative pole during electrolysis.Rana temporaria: A species of the family Ranidae occurring in a wide variety of habitats from within the Arctic Circle to South Africa, Australia, etc.Sodium Isotopes: Stable sodium atoms that have the same atomic number as the element sodium, but differ in atomic weight. Na-23 is a stable sodium isotope.Pharmacokinetics: Dynamic and kinetic mechanisms of exogenous chemical and DRUG LIBERATION; ABSORPTION; BIOLOGICAL TRANSPORT; TISSUE DISTRIBUTION; BIOTRANSFORMATION; elimination; and DRUG TOXICITY as a function of dosage, and rate of METABOLISM. LADMER, ADME and ADMET are abbreviations for liberation, absorption, distribution, metabolism, elimination, and toxicology.Lymph: The interstitial fluid that is in the LYMPHATIC SYSTEM.Porosity: Condition of having pores or open spaces. This often refers to bones, bone implants, or bone cements, but can refer to the porous state of any solid substance.Ion Channel Gating: The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability.Solubility: The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Glycols: A generic grouping for dihydric alcohols with the hydroxy groups (-OH) located on different carbon atoms. They are viscous liquids with high boiling points for their molecular weights.Claudin-3: A ubiquitously-expressed claudin subtype that acts as a general barrier-forming protein in TIGHT JUNCTIONS. Elevated expression of claudin-3 is found in a variety of tumor cell types, suggesting its role as a therapeutic target for specific ANTINEOPLASTIC AGENTS.Bufo marinus: A species of the true toads, Bufonidae, becoming fairly common in the southern United States and almost pantropical. The secretions from the skin glands of this species are very toxic to animals.Mercuric Chloride: Mercury chloride (HgCl2). A highly toxic compound that volatizes slightly at ordinary temperature and appreciably at 100 degrees C. It is corrosive to mucous membranes and used as a topical antiseptic and disinfectant.Cytochrome c Group: A group of cytochromes with covalent thioether linkages between either or both of the vinyl side chains of protoheme and the protein. (Enzyme Nomenclature, 1992, p539)Ruthenium Red: An inorganic dye used in microscopy for differential staining and as a diagnostic reagent. In research this compound is used to study changes in cytoplasmic concentrations of calcium. Ruthenium red inhibits calcium transport through membrane channels.Peritoneum: A membrane of squamous EPITHELIAL CELLS, the mesothelial cells, covered by apical MICROVILLI that allow rapid absorption of fluid and particles in the PERITONEAL CAVITY. The peritoneum is divided into parietal and visceral components. The parietal peritoneum covers the inside of the ABDOMINAL WALL. The visceral peritoneum covers the intraperitoneal organs. The double-layered peritoneum forms the MESENTERY that suspends these organs from the abdominal wall.Propidium: Quaternary ammonium analog of ethidium; an intercalating dye with a specific affinity to certain forms of DNA and, used as diiodide, to separate them in density gradients; also forms fluorescent complexes with cholinesterase which it inhibits.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Reperfusion Injury: Adverse functional, metabolic, or structural changes in ischemic tissues resulting from the restoration of blood flow to the tissue (REPERFUSION), including swelling; HEMORRHAGE; NECROSIS; and damage from FREE RADICALS. The most common instance is MYOCARDIAL REPERFUSION INJURY.Magnesium: A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.Valinomycin: A cyclododecadepsipeptide ionophore antibiotic produced by Streptomyces fulvissimus and related to the enniatins. It is composed of 3 moles each of L-valine, D-alpha-hydroxyisovaleric acid, D-valine, and L-lactic acid linked alternately to form a 36-membered ring. (From Merck Index, 11th ed) Valinomycin is a potassium selective ionophore and is commonly used as a tool in biochemical studies.Platelet Activating Factor: A phospholipid derivative formed by PLATELETS; BASOPHILS; NEUTROPHILS; MONOCYTES; and MACROPHAGES. It is a potent platelet aggregating agent and inducer of systemic anaphylactic symptoms, including HYPOTENSION; THROMBOCYTOPENIA; NEUTROPENIA; and BRONCHOCONSTRICTION.Mathematics: The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Hypertonic Solutions: Solutions that have a greater osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid.Hypotonic Solutions: Solutions that have a lesser osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid.Inflammation: A pathological process characterized by injury or destruction of tissues caused by a variety of cytologic and chemical reactions. It is usually manifested by typical signs of pain, heat, redness, swelling, and loss of function.Rhodamines: A family of 3,6-di(substituted-amino)-9-benzoate derivatives of xanthene that are used as dyes and as indicators for various metals; also used as fluorescent tracers in histochemistry.