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Bilirubin
Bilirubin (BR) (adopted from German, originally bili—bile—plus ruber—red—from Latin) is a red-orange compound that occurs in the normcomponent of the straw-yellow color in urine. Another breakdown product, stercobilin, causes the brown color of feces. Although bilirubin is usually found in animals rather than plants, at least one plant species, '' Strelitzia nicolai'', is known to contain the pigment. Structure Bilirubin consists of an open-chain tetrapyrrole. It is formed by oxidative cleavage of a porphyrin in heme, which affords biliverdin. Biliverdin is reduced to bilirubin. After conjugation with glucuronic acid, bilirubin is water-soluble and can be excreted. Bilirubin is structurally similar to the pigment phycobilin used by certain algae to capture light energy, and to the pigment phytochrome used by plants to sense light. All of these contain an open chain of four pyrrolic rings. Like these other pigments, some of the double-bonds in bilirubin isomer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jaundice
Jaundice, also known as icterus, is a yellowish or, less frequently, greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme metabolism, liver dysfunction, or biliary-tract obstruction. The prevalence of jaundice in adults is rare, while jaundice in babies is common, with an estimated 80% affected during their first week of life. The most commonly associated symptoms of jaundice are itchiness, pale feces, and dark urine. Normal levels of bilirubin in blood are below 1.0 mg/ dl (17 μmol/ L), while levels over 2–3 mg/dl (34–51 μmol/L) typically result in jaundice. High blood bilirubin is divided into two types: unconjugated and conjugated bilirubin. Causes of jaundice vary from relatively benign to potentially fatal. High unconjugated bilirubin may be due to excess red blood cell breakdown, large bruises, gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gilbert's Syndrome
Gilbert syndrome (GS) is a syndrome in which the liver of affected individuals processes bilirubin more slowly than the majority resulting in higher levels in the blood. Many people never have symptoms. Occasionally jaundice (a yellowing of the skin or whites of the eyes) may occur. Gilbert syndrome is due to a genetic variant in the ''UGT1A1'' gene which results in decreased activity of the bilirubin uridine diphosphate glucuronosyltransferase enzyme. It is typically inherited in an autosomal recessive pattern and occasionally in an autosomal dominant pattern depending on the type of variant. Episodes of jaundice may be triggered by stress such as exercise, menstruation, or not eating. Diagnosis is based on elevated levels of unconjugated bilirubin in the blood without signs of liver problems or red blood cell breakdown. Typically no treatment is needed. Phenobarbital aids in the conjugation of bilirubin and can be prescribed if jaundice becomes significant. Gilbert s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neonatal Jaundice
Neonatal jaundice is a yellowish discoloration of the white part of the eyes and skin in a newborn baby due to high bilirubin levels. Other symptoms may include excess sleepiness or poor feeding. Complications may include seizures, cerebral palsy, or kernicterus. In most of cases there is no specific underlying physiologic disorder. In other cases it results from red blood cell breakdown, liver disease, infection, hypothyroidism, or metabolic disorders (pathologic). A bilirubin level more than 34 μmol/L (2 mg/dL) may be visible. Concerns, in otherwise healthy babies, occur when levels are greater than 308 μmol/L (18 mg/dL), jaundice is noticed in the first day of life, there is a rapid rise in levels, jaundice lasts more than two weeks, or the baby appears unwell. In those with concerning findings further investigations to determine the underlying cause are recommended. The need for treatment depends on bilirubin levels, the age of the child, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crigler–Najjar Syndrome
Crigler–Najjar syndrome is a rare inherited autosomal recessive disorder affecting the metabolism of bilirubin, a chemical formed from the breakdown of the heme in red blood cells. The disorder results in a form of non hemolytic jaundice, which results in high levels of unconjugated bilirubin and often leads to brain damage in infants. The disorder is inherited in an autosomal recessive manner. The annual incidence is estimated at 0.6-1 in 1,000,000. This syndrome is divided into types I and II, with the latter sometimes called Arias syndrome. These two types, along with Gilbert's syndrome, Dubin–Johnson syndrome, and Rotor syndrome, make up the five known hereditary defects in bilirubin metabolism. Unlike Gilbert's syndrome, only a few cases of Crigler–Najjar syndrome are known. Signs and symptoms Signs and symptoms of Crigler–Najjar syndrome include jaundice, diarrhea, vomiting, fever, confusion, slurred speech, difficulty swallowing, change in gait, staggering, fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotor Syndrome
Rotor syndrome (also known as Rotor type hyperbilirubinemia) is a rare cause of mixed direct (conjugated) and indirect (unconjugated) hyperbilirubinemia, relatively benign, autosomal recessive bilirubin disorder characterized by non-hemolytic jaundice due to the chronic elevation of predominantly conjugated bilirubin. Rotor type hyperbilirubinemia is a distinct yet similar disorder to Dubin–Johnson syndrome – both diseases cause an increase in conjugated bilirubin, but Rotor syndrome differs in that it is a result of impaired hepatocellular storage of conjugated bilirubin that leaks into plasma causing hyperbilirubinemia. Signs and symptoms Rotor syndrome has many features in common with Dubin–Johnson syndrome, an exception being that the liver cells are not pigmented. The main symptom is a non-itching jaundice. There is a rise in bilirubin in the patient's serum, mainly of the conjugated type. It can be differentiated from Dubin–Johnson syndrome in the following ways: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biliverdin Reductase
Biliverdin reductase (BVR) is an enzyme () found in all tissues under normal conditions, but especially in Mononuclear phagocyte system, reticulo-macrophages of the liver and spleen. BVR facilitates the conversion of biliverdin to bilirubin via the Organic redox reaction, reduction of a double bond between the second and third pyrrole ring into a single bond. There are two isozymes in humans, each encoded by its own gene, biliverdin reductase A (BLVRA) and biliverdin reductase B (BLVRB). Mechanism of catalysis BVR acts on biliverdin by reducing its double-bond between the pyrrole rings into a single-bond. It accomplishes this using NADPH + H+ as an electron donor, forming bilirubin and NADP+ as products. BVR catalyzes this reaction through an overlapping binding site including Lys18, Lys22, Lys179, Arg183, and Arg185 as key residues. This binding site attaches to biliverdin, and causes its dissociation from heme oxygenase (HO) (which catalyzes reaction of ferric heme --> b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uridine Diphosphate Glucuronyltransferase
Uridine 5'-diphospho-glucuronosyltransferase ( UDP-glucuronosyltransferase, UDPGT or UGT) is a microsomal glycosyltransferase () that catalyzes the transfer of the glucuronic acid component of UDP-glucuronic acid to a small hydrophobic molecule. This is a glucuronidation reaction. ''Alternative names:'' * glucuronyltransferase * UDP-glucuronyl transferase * UDP-GT Function Glucuronosyltransferases are responsible for the process of glucuronidation, a major part of phase II metabolism. Arguably the most important of the Phase II (conjugative) enzymes, UGTs have been the subject of increasing scientific inquiry since the mid-to-late 1990s. The reaction catalyzed by the UGT enzyme involves the addition of a glucuronic acid moiety to xenobiotics and is the most important pathway for the human body's elimination of the most frequently prescribed drugs. It is also the major pathway for foreign chemical (dietary, environmental, pharmaceutical) removal for most drugs, dietary substa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dubin–Johnson Syndrome
Dubin–Johnson syndrome is a rare, autosomal recessive, benign disorder that causes an isolated increase of conjugated bilirubin in the serum. Classically, the condition causes a black liver due to the deposition of a pigment similar to melanin. This condition is associated with a defect in the ability of hepatocytes to secrete conjugated bilirubin into the bile, and is similar to Rotor syndrome. It is usually asymptomatic, but may be diagnosed in early infancy based on laboratory tests. No treatment is usually needed. Signs and Symptoms In the majority of patients with this syndrome, they lack overt signs and are incidentally diagnosed during routine laboratory tests with isolated conjugated hyperbilirubinemia despite normal liver enzymes and otherwise normal liver function. When symptoms do appear, they may be generalized weakness, nonspecific stomach pain, yellowing of the skin and eyes (jaundice), and darkening of the urine. Around 80 to 99% of people with Dubin–Johnson s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heme Breakdown
Heme (American English), or haem (Commonwealth English, both pronounced / hi:m/ ), is a ring-shaped iron-containing molecule that commonly serves as a ligand of various proteins, more notably as a component of hemoglobin, which is necessary to bind oxygen in the bloodstream. It is composed of four pyrrole rings with 2 vinyl and 2 propionic acid side chains. Heme is biosynthesized in both the bone marrow and the liver. Heme plays a critical role in multiple different redox reactions in mammals, due to its ability to carry the oxygen molecule. Reactions include oxidative metabolism (cytochrome c oxidase, succinate dehydrogenase), xenobiotic detoxification via cytochrome P450 pathways (including metabolism of some drugs), gas sensing ( guanyl cyclases, nitric oxide synthase), and microRNA processing (DGCR8). Heme is a coordination complex "consisting of an iron ion coordinated to a tetrapyrrole acting as a tetradentate ligand, and to one or two axial ligands". The definition is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urobilinogen
Urobilinogen is a yellow by-product of bilirubin reduction. It is formed in the intestines by the bacterial enzyme bilirubin reductase. About half of the urobilinogen formed is reabsorbed and taken up via the portal vein to the liver, enters circulation and is excreted by the kidney. Increased amounts of bilirubin are formed in hemolysis, which generates increased urobilinogen in the gut. In liver disease (such as hepatitis), the intrahepatic urobilinogen cycle is inhibited also increasing urobilinogen levels. Urobilinogen is converted to the yellow pigmented urobilin apparent in urine. The urobilinogen in the intestine is directly reduced to brownish colour stercobilin, which gives the feces their characteristic color. It can also be reduced to stercobilinogen, which can then be further oxidized to stercobilin. In biliary obstruction, below-normal amounts of conjugated bilirubin reach the intestine for conversion to urobilinogen. With limited urobilinogen available for reabsorpt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
