Bilirubin: A bile pigment that is a degradation product of HEME.Hyperbilirubinemia: A condition characterized by an abnormal increase of BILIRUBIN in the blood, which may result in JAUNDICE. Bilirubin, a breakdown product of HEME, is normally excreted in the BILE or further catabolized before excretion in the urine.Jaundice, Neonatal: Yellow discoloration of the SKIN; MUCOUS MEMBRANE; and SCLERA in the NEWBORN. It is a sign of NEONATAL HYPERBILIRUBINEMIA. Most cases are transient self-limiting (PHYSIOLOGICAL NEONATAL JAUNDICE) occurring in the first week of life, but some can be a sign of pathological disorders, particularly LIVER DISEASES.Rats, Gunn: Mutant strain of Rattus norvegicus which is used as a disease model of kernicterus.Bile Pigments: Linear TETRAPYRROLES that give a characteristic color to BILE including: BILIRUBIN; BILIVERDIN; and bilicyanin.Kernicterus: A term used pathologically to describe BILIRUBIN staining of the BASAL GANGLIA; BRAIN STEM; and CEREBELLUM and clinically to describe a syndrome associated with HYPERBILIRUBINEMIA. Clinical features include athetosis, MUSCLE SPASTICITY or hypotonia, impaired vertical gaze, and DEAFNESS. Nonconjugated bilirubin enters the brain and acts as a neurotoxin, often in association with conditions that impair the BLOOD-BRAIN BARRIER (e.g., SEPSIS). This condition occurs primarily in neonates (INFANT, NEWBORN), but may rarely occur in adults. (Menkes, Textbook of Child Neurology, 5th ed, p613)Jaundice: A clinical manifestation of HYPERBILIRUBINEMIA, characterized by the yellowish staining of the SKIN; MUCOUS MEMBRANE; and SCLERA. Clinical jaundice usually is a sign of LIVER dysfunction.Hyperbilirubinemia, Neonatal: Accumulation of BILIRUBIN, a breakdown product of HEME PROTEINS, in the BLOOD during the first weeks of life. This may lead to NEONATAL JAUNDICE. The excess bilirubin may exist in the unconjugated (indirect) or the conjugated (direct) form. The condition may be self-limiting (PHYSIOLOGICAL NEONATAL JAUNDICE) or pathological with toxic levels of bilirubin.Hyperbilirubinemia, Hereditary: Inborn errors of bilirubin metabolism resulting in excessive amounts of bilirubin in the circulating blood, either because of increased bilirubin production or because of delayed clearance of bilirubin from the blood.Glucuronosyltransferase: A family of enzymes accepting a wide range of substrates, including phenols, alcohols, amines, and fatty acids. They function as drug-metabolizing enzymes that catalyze the conjugation of UDPglucuronic acid to a variety of endogenous and exogenous compounds. EC CompoundsBiliverdine: 1,3,6,7-Tetramethyl-4,5-dicarboxyethyl-2,8-divinylbilenone. Biosynthesized from hemoglobin as a precursor of bilirubin. Occurs in the bile of AMPHIBIANS and of birds, but not in normal human bile or serum.Crigler-Najjar Syndrome: A familial form of congenital hyperbilirubinemia transmitted as an autosomal recessive trait. It is characterized by icterus and brain damage caused by a glucuronyl transferase deficiency in the liver and faulty bilirubin conjugation.Gilbert Disease: A benign familial disorder, transmitted as an autosomal dominant trait. It is characterized by low-grade chronic hyperbilirubinemia with considerable daily fluctuations of the bilirubin level.Phototherapy: Treatment of disease by exposure to light, especially by variously concentrated light rays or specific wavelengths.Bile: An emulsifying agent produced in the LIVER and secreted into the DUODENUM. Its composition includes BILE ACIDS AND SALTS; CHOLESTEROL; and ELECTROLYTES. It aids DIGESTION of fats in the duodenum.Serum Albumin: A major protein in the BLOOD. It is important in maintaining the colloidal osmotic pressure and transporting large organic molecules.Glucuronates: Derivatives of GLUCURONIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that include the 6-carboxy glucose structure.Azo CompoundsLiver Function Tests: Blood tests that are used to evaluate how well a patient's liver is working and also to help diagnose liver conditions.Oxidoreductases Acting on CH-CH Group Donors: A subclass of enzymes which includes all dehydrogenases acting on carbon-carbon bonds. This enzyme group includes all the enzymes that introduce double bonds into substrates by direct dehydrogenation of carbon-carbon single bonds.Cholestasis: Impairment of bile flow due to obstruction in small bile ducts (INTRAHEPATIC CHOLESTASIS) or obstruction in large bile ducts (EXTRAHEPATIC CHOLESTASIS).Autoanalysis: Method of analyzing chemicals using automation.Sulfanilic Acids: Aminobenzenesulfonic acids. Organic acids that are used in the manufacture of dyes and organic chemicals and as reagents.Heme Oxygenase (Decyclizing): A mixed function oxidase enzyme which during hemoglobin catabolism catalyzes the degradation of heme to ferrous iron, carbon monoxide and biliverdin in the presence of molecular oxygen and reduced NADPH. The enzyme is induced by metals, particularly cobalt. EC A phenolphthalein that is used as a diagnostic aid in hepatic function determination.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Urobilinogen: A colorless compound formed in the intestines by the reduction of bilirubin. Some is excreted in the feces where it is oxidized to urobilin. Some is reabsorbed and re-excreted in the bile as bilirubin. At times, it is re-excreted in the urine, where it may be later oxidized to urobilin.Spectrophotometry: The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.Infant, Newborn: An infant during the first month after birth.Aspartate Aminotransferases: Enzymes of the transferase class that catalyze the conversion of L-aspartate and 2-ketoglutarate to oxaloacetate and L-glutamate. EC Oxygenase-1: A ubiquitous stress-responsive enzyme that catalyzes the oxidative cleavage of HEME to yield IRON; CARBON MONOXIDE; and BILIVERDIN.Alanine Transaminase: An enzyme that catalyzes the conversion of L-alanine and 2-oxoglutarate to pyruvate and L-glutamate. (From Enzyme Nomenclature, 1992) EC Diseases: Pathological processes of the LIVER.Chloroform: A commonly used laboratory solvent. It was previously used as an anesthetic, but was banned from use in the U.S. due to its suspected carcinogenicity.Neonatal Screening: The identification of selected parameters in newborn infants by various tests, examinations, or other procedures. Screening may be performed by clinical or laboratory measures. A screening test is designed to sort out healthy neonates (INFANT, NEWBORN) from those not well, but the screening test is not intended as a diagnostic device, rather instead as epidemiologic.Uridine Diphosphate Glucuronic Acid: A nucleoside diphosphate sugar which serves as a source of glucuronic acid for polysaccharide biosynthesis. It may also be epimerized to UDP iduronic acid, which donates iduronic acid to polysaccharides. In animals, UDP glucuronic acid is used for formation of many glucosiduronides with various aglycones.Indicators and Reagents: Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)