Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Kidney Diseases: Pathological processes of the KIDNEY or its component tissues.Kidney Transplantation: The transference of a kidney from one human or animal to another.Kidney Tubules: Long convoluted tubules in the nephrons. They collect filtrate from blood passing through the KIDNEY GLOMERULUS and process this filtrate into URINE. Each renal tubule consists of a BOWMAN CAPSULE; PROXIMAL KIDNEY TUBULE; LOOP OF HENLE; DISTAL KIDNEY TUBULE; and KIDNEY COLLECTING DUCT leading to the central cavity of the kidney (KIDNEY PELVIS) that connects to the URETER.Kidney Cortex: The outer zone of the KIDNEY, beneath the capsule, consisting of KIDNEY GLOMERULUS; KIDNEY TUBULES, DISTAL; and KIDNEY TUBULES, PROXIMAL.Acute Kidney Injury: Abrupt reduction in kidney function. Acute kidney injury encompasses the entire spectrum of the syndrome including acute kidney failure; ACUTE KIDNEY TUBULAR NECROSIS; and other less severe conditions.Kidney Failure, Chronic: The end-stage of CHRONIC RENAL INSUFFICIENCY. It is characterized by the severe irreversible kidney damage (as measured by the level of PROTEINURIA) and the reduction in GLOMERULAR FILTRATION RATE to less than 15 ml per min (Kidney Foundation: Kidney Disease Outcome Quality Initiative, 2002). These patients generally require HEMODIALYSIS or KIDNEY TRANSPLANTATION.Polycystic Kidney Diseases: Hereditary diseases that are characterized by the progressive expansion of a large number of tightly packed CYSTS within the KIDNEYS. They include diseases with autosomal dominant and autosomal recessive inheritance.Kidney Glomerulus: A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue.Kidney Neoplasms: Tumors or cancers of the KIDNEY.Kidney Tubules, Proximal: The renal tubule portion that extends from the BOWMAN CAPSULE in the KIDNEY CORTEX into the KIDNEY MEDULLA. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the U-shaped LOOP OF HENLE.Kidney Function Tests: Laboratory tests used to evaluate how well the kidneys are working through examination of blood and urine.Kidney Medulla: The internal portion of the kidney, consisting of striated conical masses, the renal pyramids, whose bases are adjacent to the cortex and whose apices form prominent papillae projecting into the lumen of the minor calyces.Kidney Calculi: Stones in the KIDNEY, usually formed in the urine-collecting area of the kidney (KIDNEY PELVIS). Their sizes vary and most contains CALCIUM OXALATE.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.Polycystic Kidney, Autosomal Dominant: Kidney disorders with autosomal dominant inheritance and characterized by multiple CYSTS in both KIDNEYS with progressive deterioration of renal function.Glomerular Filtration Rate: The volume of water filtered out of plasma through glomerular capillary walls into Bowman's capsules per unit of time. It is considered to be equivalent to INULIN clearance.Kidney Diseases, Cystic: A heterogeneous group of hereditary and acquired disorders in which the KIDNEY contains one or more CYSTS unilaterally or bilaterally (KIDNEY, CYSTIC).Kidney Concentrating Ability: The ability of the kidney to excrete in the urine high concentrations of solutes from the blood plasma.Kidney Tubules, Distal: The portion of renal tubule that begins from the enlarged segment of the ascending limb of the LOOP OF HENLE. It reenters the KIDNEY CORTEX and forms the convoluted segments of the distal tubule.CreatinineNephrectomy: Excision of kidney.Nephrons: The functional units of the kidney, consisting of the glomerulus and the attached tubule.Tissue Distribution: Accumulation of a drug or chemical substance in various organs (including those not relevant to its pharmacologic or therapeutic action). This distribution depends on the blood flow or perfusion rate of the organ, the ability of the drug to penetrate organ membranes, tissue specificity, protein binding. The distribution is usually expressed as tissue to plasma ratios.Kidney Tubular Necrosis, Acute: Acute kidney failure resulting from destruction of EPITHELIAL CELLS of the KIDNEY TUBULES. It is commonly attributed to exposure to toxic agents or renal ISCHEMIA following severe TRAUMA.Ureter: One of a pair of thick-walled tubes that transports urine from the KIDNEY PELVIS to the URINARY BLADDER.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)Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Proteinuria: The presence of proteins in the urine, an indicator of KIDNEY DISEASES.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Multicystic Dysplastic Kidney: A nongenetic defect due to malformation of the KIDNEY which appears as a bunch of grapes with multiple renal cysts but lacking the normal renal bean shape, and the collection drainage system. This condition can be detected in-utero with ULTRASONOGRAPHY.Cell Line: Established cell cultures that have the potential to propagate indefinitely.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.Polycystic Kidney, Autosomal Recessive: A genetic disorder with autosomal recessive inheritance, characterized by multiple CYSTS in both KIDNEYS and associated LIVER lesions. Serious manifestations are usually present at BIRTH with high PERINATAL MORTALITY.Tissue Donors: Individuals supplying living tissue, organs, cells, blood or blood components for transfer or transplantation to histocompatible recipients.Graft Rejection: An immune response with both cellular and humoral components, directed against an allogeneic transplant, whose tissue antigens are not compatible with those of the recipient.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.Kidneys, Artificial: Devices which can substitute for normally functioning KIDNEYS in removing components from the blood by DIALYSIS that are normally eliminated in the URINE.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.Ureteral Obstruction: Blockage in any part of the URETER causing obstruction of urine flow from the kidney to the URINARY BLADDER. The obstruction may be congenital, acquired, unilateral, bilateral, complete, partial, acute, or chronic. Depending on the degree and duration of the obstruction, clinical features vary greatly such as HYDRONEPHROSIS and obstructive nephropathy.TRPP Cation Channels: A subgroup of TRP cation channels that are widely expressed in various cell types. Defects are associated with POLYCYSTIC KIDNEY DISEASES.Renal Circulation: The circulation of the BLOOD through the vessels of the KIDNEY.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Living Donors: Non-cadaveric providers of organs for transplant to related or non-related recipients.Diabetic Nephropathies: KIDNEY injuries associated with diabetes mellitus and affecting KIDNEY GLOMERULUS; ARTERIOLES; KIDNEY TUBULES; and the interstitium. Clinical signs include persistent PROTEINURIA, from microalbuminuria progressing to ALBUMINURIA of greater than 300 mg/24 h, leading to reduced GLOMERULAR FILTRATION RATE and END-STAGE RENAL DISEASE.Organ Specificity: Characteristic restricted to a particular organ of the body, such as a cell type, metabolic response or expression of a particular protein or antigen.Renal Insufficiency: Conditions in which the KIDNEYS perform below the normal level in the ability to remove wastes, concentrate URINE, and maintain ELECTROLYTE BALANCE; BLOOD PRESSURE; and CALCIUM metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of PROTEINURIA) and reduction in GLOMERULAR FILTRATION RATE.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.Chronic Disease: Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care. (Dictionary of Health Services Management, 2d ed)Hydronephrosis: Abnormal enlargement or swelling of a KIDNEY due to dilation of the KIDNEY CALICES and the KIDNEY PELVIS. It is often associated with obstruction of the URETER or chronic kidney diseases that prevents normal drainage of urine into the URINARY BLADDER.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.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.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Tissue and Organ Procurement: The administrative procedures involved with acquiring TISSUES or organs for TRANSPLANTATION through various programs, systems, or organizations. These procedures include obtaining consent from TISSUE DONORS and arranging for transportation of donated tissues and organs, after TISSUE HARVESTING, to HOSPITALS for processing and transplantation.Immunosuppressive Agents: Agents that suppress immune function by one of several mechanisms of action. Classical cytotoxic immunosuppressants act by inhibiting DNA synthesis. Others may act through activation of T-CELLS or by inhibiting the activation of HELPER CELLS. While immunosuppression has been brought about in the past primarily to prevent rejection of transplanted organs, new applications involving mediation of the effects of INTERLEUKINS and other CYTOKINES are emerging.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.Nephritis: Inflammation of any part of the KIDNEY.Renal Dialysis: Therapy for the insufficient cleansing of the BLOOD by the kidneys based on dialysis and including hemodialysis, PERITONEAL DIALYSIS, and HEMODIAFILTRATION.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.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Albuminuria: The presence of albumin in the urine, an indicator of KIDNEY DISEASES.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Cadaver: A dead body, usually a human body.Nephrology: A subspecialty of internal medicine concerned with the anatomy, physiology, and pathology of the kidney.Organ Size: The measurement of an organ in volume, mass, or heaviness.Podocytes: Highly differentiated epithelial cells of the visceral layer of BOWMAN CAPSULE of the KIDNEY. They are composed of a cell body with major CELL SURFACE EXTENSIONS and secondary fingerlike extensions called pedicels. They enwrap the KIDNEY GLOMERULUS capillaries with their cell surface extensions forming a filtration structure. The pedicels of neighboring podocytes interdigitate with each other leaving between them filtration slits that are bridged by an extracellular structure impermeable to large macromolecules called the slit diaphragm, and provide the last barrier to protein loss in the KIDNEY.Kidney Cortex Necrosis: Death of cells in the KIDNEY CORTEX, a common final result of various renal injuries including HYPOXIA; ISCHEMIA; and drug toxicity.Delayed Graft Function: General dysfunction of an organ occurring immediately following its transplantation. The term most frequently refers to renal dysfunction following KIDNEY TRANSPLANTATION.Mice, Inbred C57BLBlood Urea Nitrogen: The urea concentration of the blood stated in terms of nitrogen content. Serum (plasma) urea nitrogen is approximately 12% higher than blood urea nitrogen concentration because of the greater protein content of red blood cells. Increases in blood or serum urea nitrogen are referred to as azotemia and may have prerenal, renal, or postrenal causes. (From Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984)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.Pancreas Transplantation: The transference of a pancreas from one human or animal to another.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Cystatin C: An extracellular cystatin subtype that is abundantly expressed in bodily fluids. It may play a role in the inhibition of interstitial CYSTEINE PROTEASES.Nephritis, Interstitial: Inflammation of the interstitial tissue of the kidney. This term is generally used for primary inflammation of KIDNEY TUBULES and/or surrounding interstitium. For primary inflammation of glomerular interstitium, see GLOMERULONEPHRITIS. Infiltration of the inflammatory cells into the interstitial compartment results in EDEMA, increased spaces between the tubules, and tubular renal dysfunction.Renin: A highly specific (Leu-Leu) endopeptidase that generates ANGIOTENSIN I from its precursor ANGIOTENSINOGEN, leading to a cascade of reactions which elevate BLOOD PRESSURE and increase sodium retention by the kidney in the RENIN-ANGIOTENSIN SYSTEM. The enzyme was formerly listed as EC 184.108.40.206.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.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Glomerulonephritis: Inflammation of the renal glomeruli (KIDNEY GLOMERULUS) that can be classified by the type of glomerular injuries including antibody deposition, complement activation, cellular proliferation, and glomerulosclerosis. These structural and functional abnormalities usually lead to HEMATURIA; PROTEINURIA; HYPERTENSION; and RENAL INSUFFICIENCY.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.Uromodulin: A glycosyl-phosphatidyl-inositol (GPI) - anchored membrane protein found on the thick ascending limb of the LOOP OF HENLE. The cleaved form of the protein is found abundantly in URINE.Hypertension, Renal: Persistent high BLOOD PRESSURE due to KIDNEY DISEASES, such as those involving the renal parenchyma, the renal vasculature, or tumors that secrete RENIN.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Hypertension: Persistently high systemic arterial BLOOD PRESSURE. Based on multiple readings (BLOOD PRESSURE DETERMINATION), hypertension is currently defined as when SYSTOLIC PRESSURE is consistently greater than 140 mm Hg or when DIASTOLIC PRESSURE is consistently 90 mm Hg or more.Organ Preservation: The process by which organs are kept viable outside of the organism from which they were removed (i.e., kept from decay by means of a chemical agent, cooling, or a fluid substitute that mimics the natural state within the organism).Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Glomerulosclerosis, Focal Segmental: A clinicopathological syndrome or diagnostic term for a type of glomerular injury that has multiple causes, primary or secondary. Clinical features include PROTEINURIA, reduced GLOMERULAR FILTRATION RATE, and EDEMA. Kidney biopsy initially indicates focal segmental glomerular consolidation (hyalinosis) or scarring which can progress to globally sclerotic glomeruli leading to eventual KIDNEY FAILURE.Disease Progression: The worsening of a disease over time. This concept is most often used for chronic and incurable diseases where the stage of the disease is an important determinant of therapy and prognosis.Opossums: New World marsupials of the family Didelphidae. Opossums are omnivorous, largely nocturnal and arboreal MAMMALS, grow to about three feet in length, including the scaly prehensile tail, and have an abdominal pouch in which the young are carried at birth.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Kidney Calices: Recesses of the kidney pelvis which divides into two wide, cup-shaped major renal calices, with each major calix subdivided into 7 to 14 minor calices. Urine empties into a minor calix from collecting tubules, then passes through the major calix, renal pelvis, and ureter to enter the urinary bladder. (From Moore, Clinically Oriented Anatomy, 3d ed, p211)Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Radioisotope Renography: Graphic tracing over a time period of radioactivity measured externally over the kidneys following intravenous injection of a radionuclide which is taken up and excreted by the kidneys.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.Renal Replacement Therapy: Procedures which temporarily or permanently remedy insufficient cleansing of body fluids by the kidneys.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.Kinetics: The rate dynamics in chemical or physical systems.Carcinoma, Renal Cell: A heterogeneous group of sporadic or hereditary carcinoma derived from cells of the KIDNEYS. There are several subtypes including the clear cells, the papillary, the chromophobe, the collecting duct, the spindle cells (sarcomatoid), or mixed cell-type carcinoma.Hypertension, Renovascular: Hypertension due to RENAL ARTERY OBSTRUCTION or compression.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.DNA, Complementary: Single-stranded complementary DNA synthesized from an RNA template by the action of RNA-dependent DNA polymerase. cDNA (i.e., complementary DNA, not circular DNA, not C-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe.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.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.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.Aquaporin 2: Aquaporin 2 is a water-specific channel protein that is expressed in KIDNEY COLLECTING DUCTS. The translocation of aquaporin 2 to the apical PLASMA MEMBRANE is regulated by VASOPRESSIN, and MUTATIONS in AQP2 have been implicated in a variety of kidney disorders including DIABETES INSIPIDUS.Ischemia: A hypoperfusion of the BLOOD through an organ or tissue caused by a PATHOLOGIC CONSTRICTION or obstruction of its BLOOD VESSELS, or an absence of BLOOD CIRCULATION.Pyelonephritis: Inflammation of the KIDNEY involving the renal parenchyma (the NEPHRONS); KIDNEY PELVIS; and KIDNEY CALICES. It is characterized by ABDOMINAL PAIN; FEVER; NAUSEA; VOMITING; and occasionally DIARRHEA.Transplantation, Homologous: Transplantation between individuals of the same species. Usually refers to genetically disparate individuals in contradistinction to isogeneic transplantation for genetically identical individuals.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.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.Sodium-Potassium-Exchanging ATPase: An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.Epithelium: One or more layers of EPITHELIAL CELLS, supported by the basal lamina, which covers the inner or outer surfaces of the body.Loop of Henle: The U-shaped portion of the renal tubule in the KIDNEY MEDULLA, consisting of a descending limb and an ascending limb. It is situated between the PROXIMAL KIDNEY TUBULE and the DISTAL KIDNEY TUBULE.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.Renal Artery Obstruction: Narrowing or occlusion of the RENAL ARTERY or arteries. It is due usually to ATHEROSCLEROSIS; FIBROMUSCULAR DYSPLASIA; THROMBOSIS; EMBOLISM, or external pressure. The reduced renal perfusion can lead to renovascular hypertension (HYPERTENSION, RENOVASCULAR).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.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Biopsy: Removal and pathologic examination of specimens in the form of small pieces of tissue from the living body.PAX2 Transcription Factor: A paired box transcription factor that is essential for ORGANOGENESIS of the CENTRAL NERVOUS SYSTEM and KIDNEY.Carrier Proteins: Transport proteins that carry specific substances in the blood or across cell membranes.Microvilli: Minute projections of cell membranes which greatly increase the surface area of the cell.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Renin-Angiotensin System: A BLOOD PRESSURE regulating system of interacting components that include RENIN; ANGIOTENSINOGEN; ANGIOTENSIN CONVERTING ENZYME; ANGIOTENSIN I; ANGIOTENSIN II; and angiotensinase. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming ANGIOTENSIN I. Angiotensin-converting enzyme, contained in the lung, acts on angiotensin I in the plasma converting it to ANGIOTENSIN II, an extremely powerful vasoconstrictor. Angiotensin II causes contraction of the arteriolar and renal VASCULAR SMOOTH MUSCLE, leading to retention of salt and water in the KIDNEY and increased arterial blood pressure. In addition, angiotensin II stimulates the release of ALDOSTERONE from the ADRENAL CORTEX, which in turn also increases salt and water retention in the kidney. Angiotensin-converting enzyme also breaks down BRADYKININ, a powerful vasodilator and component of the KALLIKREIN-KININ SYSTEM.Diuresis: An increase in the excretion of URINE. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Donor Selection: The procedure established to evaluate the health status and risk factors of the potential DONORS of biological materials. Donors are selected based on the principles that their health will not be compromised in the process, and the donated materials, such as TISSUES or organs, are safe for reuse in the recipients.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.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).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.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.Cohort Studies: Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.Urine: Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the URETHRA.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Cysts: Any fluid-filled closed cavity or sac that is lined by an EPITHELIUM. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues.Angiotensin II: An octapeptide that is a potent but labile vasoconstrictor. It is produced from angiotensin I after the removal of two amino acids at the C-terminal by ANGIOTENSIN CONVERTING ENZYME. The amino acid in position 5 varies in different species. To block VASOCONSTRICTION and HYPERTENSION effect of angiotensin II, patients are often treated with ACE INHIBITORS or with ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKERS.Parathyroid Hormone: A polypeptide hormone (84 amino acid residues) secreted by the PARATHYROID GLANDS which performs the essential role of maintaining intracellular CALCIUM levels in the body. Parathyroid hormone increases intracellular calcium by promoting the release of CALCIUM from BONE, increases the intestinal absorption of calcium, increases the renal tubular reabsorption of calcium, and increases the renal excretion of phosphates.Diabetes Mellitus, Experimental: Diabetes mellitus induced experimentally by administration of various diabetogenic agents or by PANCREATECTOMY.Blotting, Northern: Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Microsomes: Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Juxtaglomerular Apparatus: A complex of cells consisting of juxtaglomerular cells, extraglomerular mesangium lacis cells, the macula densa of the distal convoluted tubule, and granular epithelial peripolar cells. Juxtaglomerular cells are modified SMOOTH MUSCLE CELLS found in the walls of afferent glomerular arterioles and sometimes the efferent arterioles. Extraglomerular mesangium lacis cells are located in the angle between the afferent and efferent glomerular arterioles. Granular epithelial peripolar cells are located at the angle of reflection of the parietal to visceral angle of the renal corpuscle.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.Madin Darby Canine Kidney Cells: An epithelial cell line derived from a kidney of a normal adult female dog.Nephrosclerosis: Hardening of the KIDNEY due to infiltration by fibrous connective tissue (FIBROSIS), usually caused by renovascular diseases or chronic HYPERTENSION. Nephrosclerosis leads to renal ISCHEMIA.Risk Assessment: The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)Medullary Sponge Kidney: A non-hereditary KIDNEY disorder characterized by the abnormally dilated (ECTASIA) medullary and inner papillary portions of the collecting ducts. These collecting ducts usually contain CYSTS or DIVERTICULA filled with jelly-like material or small calculi (KIDNEY STONES) leading to infections or obstruction. It should be distinguished from congenital or hereditary POLYCYSTIC KIDNEY DISEASES.Waiting Lists: Prospective patient listings for appointments or treatments.AIDS-Associated Nephropathy: Renal syndrome in human immunodeficiency virus-infected patients characterized by nephrotic syndrome, severe proteinuria, focal and segmental glomerulosclerosis with distinctive tubular and interstitial changes, enlarged kidneys, and peculiar tubuloreticular structures. The syndrome is distinct from heroin-associated nephropathy as well as other forms of kidney disease seen in HIV-infected patients.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.Phosphates: Inorganic salts of phosphoric acid.Urinary Tract: The duct which coveys URINE from the pelvis of the KIDNEY through the URETERS, BLADDER, and URETHRA.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.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Tacrolimus: A macrolide isolated from the culture broth of a strain of Streptomyces tsukubaensis that has strong immunosuppressive activity in vivo and prevents the activation of T-lymphocytes in response to antigenic or mitogenic stimulation in vitro.Haplorhini: A suborder of PRIMATES consisting of six families: CEBIDAE (some New World monkeys), ATELIDAE (some New World monkeys), CERCOPITHECIDAE (Old World monkeys), HYLOBATIDAE (gibbons and siamangs), CALLITRICHINAE (marmosets and tamarins), and HOMINIDAE (humans and great apes).DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Wilms Tumor: A malignant kidney tumor, caused by the uncontrolled multiplication of renal stem (blastemal), stromal (STROMAL CELLS), and epithelial (EPITHELIAL CELLS) elements. However, not all three are present in every case. Several genes or chromosomal areas have been associated with Wilms tumor which is usually found in childhood as a firm lump in a child's side or ABDOMEN.Aquaporin 6: Aquaporin 6 is an aquaglyceroporin that is found primarily in KIDNEY COLLECTING DUCTS. AQP6 protein functions as an anion-selective channel.Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.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.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Technetium Tc 99m Mertiatide: A technetium diagnostic aid used in renal function determination.Acute-Phase Proteins: Proteins that are secreted into the blood in increased or decreased quantities by hepatocytes in response to trauma, inflammation, or disease. These proteins can serve as inhibitors or mediators of the inflammatory processes. Certain acute-phase proteins have been used to diagnose and follow the course of diseases or as tumor markers.Calcium Oxalate: The calcium salt of oxalic acid, occurring in the urine as crystals and in certain calculi.Lupus Nephritis: Glomerulonephritis associated with autoimmune disease SYSTEMIC LUPUS ERYTHEMATOSUS. Lupus nephritis is histologically classified into 6 classes: class I - normal glomeruli, class II - pure mesangial alterations, class III - focal segmental glomerulonephritis, class IV - diffuse glomerulonephritis, class V - diffuse membranous glomerulonephritis, and class VI - advanced sclerosing glomerulonephritis (The World Health Organization classification 1982).Aquaporins: A class of porins that allow the passage of WATER and other small molecules across CELL MEMBRANES.Uremia: A clinical syndrome associated with the retention of renal waste products or uremic toxins in the blood. It is usually the result of RENAL INSUFFICIENCY. Most uremic toxins are end products of protein or nitrogen CATABOLISM, such as UREA or CREATININE. Severe uremia can lead to multiple organ dysfunctions with a constellation of symptoms.Urinalysis: Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically.Isoenzymes: Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Nephrolithiasis: Formation of stones in the KIDNEY.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.Oxidative Stress: A disturbance in the prooxidant-antioxidant balance in favor of the former, leading to potential damage. Indicators of oxidative stress include damaged DNA bases, protein oxidation products, and lipid peroxidation products (Sies, Oxidative Stress, 1991, pxv-xvi).Incidence: The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from PREVALENCE, which refers to all cases, new or old, in the population at a given time.Mice, 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. All animals within an inbred strain trace back to a common ancestor in the twentieth generation.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Mycophenolic Acid: An antibiotic substance derived from Penicillium stoloniferum, and related species. It blocks de novo biosynthesis of purine nucleotides by inhibition of the enzyme inosine monophosphate dehydrogenase. Mycophenolic acid is important because of its selective effects on the immune system. It prevents the proliferation of T-cells, lymphocytes, and the formation of antibodies from B-cells. It also may inhibit recruitment of leukocytes to inflammatory sites. (From Gilman et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, p1301)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.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Basement Membrane: A darkly stained mat-like EXTRACELLULAR MATRIX (ECM) that separates cell layers, such as EPITHELIUM from ENDOTHELIUM or a layer of CONNECTIVE TISSUE. The ECM layer that supports an overlying EPITHELIUM or ENDOTHELIUM is called basal lamina. Basement membrane (BM) can be formed by the fusion of either two adjacent basal laminae or a basal lamina with an adjacent reticular lamina of connective tissue. BM, composed mainly of TYPE IV COLLAGEN; glycoprotein LAMININ; and PROTEOGLYCAN, provides barriers as well as channels between interacting cell layers.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.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.Prognosis: A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.p-Aminohippuric Acid: The glycine amide of 4-aminobenzoic acid. Its sodium salt is used as a diagnostic aid to measure effective renal plasma flow (ERPF) and excretory capacity.Directed Tissue Donation: Tissue, organ, or gamete donation intended for a designated recipient.Rats, Inbred F344Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Natriuresis: Sodium excretion by URINATION.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.Age Factors: Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.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.Hypertrophy: General increase in bulk of a part or organ due to CELL ENLARGEMENT and accumulation of FLUIDS AND SECRETIONS, not due to tumor formation, nor to an increase in the number of cells (HYPERPLASIA).Cilia: Populations of thin, motile processes found covering the surface of ciliates (CILIOPHORA) or the free surface of the cells making up ciliated EPITHELIUM. Each cilium arises from a basic granule in the superficial layer of CYTOPLASM. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Brain Death: A state of prolonged irreversible cessation of all brain activity, including lower brain stem function with the complete absence of voluntary movements, responses to stimuli, brain stem reflexes, and spontaneous respirations. Reversible conditions which mimic this clinical state (e.g., sedative overdose, hypothermia, etc.) are excluded prior to making the determination of brain death. (From Adams et al., Principles of Neurology, 6th ed, pp348-9)Phosphorus: A non-metal element that has the atomic symbol P, atomic number 15, and atomic weight 31. It is an essential element that takes part in a broad variety of biochemical reactions.Angiotensin-Converting Enzyme Inhibitors: A class of drugs whose main indications are the treatment of hypertension and heart failure. They exert their hemodynamic effect mainly by inhibiting the renin-angiotensin system. They also modulate sympathetic nervous system activity and increase prostaglandin synthesis. They cause mainly vasodilation and mild natriuresis without affecting heart rate and contractility.