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Adenosine
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA), which are essential for all life. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Adenosine is used as an intravenous medication for some cardiac arrhythmias. Adenosyl (abbreviated Ado or 5'-dAdo) is the chemical group formed by removal of the 5′-hydroxy (OH) group. It is found in adenosylcobalamin (an active form of vitamin B12) and as a radical in radical SAM enzymes. Medical uses Supraventricular tachycardia In individuals with supraventricular tachycardia (SVT), adenosine is used to help identify and convert t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenosine Triphosphate
Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer. When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. The human body recycles its own body weight equivalent in ATP each day. It is also a precursor to DNA and RNA, and is used as a coenzyme. From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base ( adenine), the sugar ribose, and the triphosphate. Structure ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar ( ribose), which in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deoxyadenosine
Deoxyadenosine (symbol dA or dAdo) is a deoxyribonucleoside. It is a derivative of the nucleoside adenosine, differing from the latter by the replacement of a hydroxyl group (-OH) by hydrogen (-H) at the 2′ position of its ribose sugar moiety. Deoxyadenosine is the DNA nucleoside A, which pairs with deoxythymidine (T) in double-stranded DNA. In absence of adenosine deaminase (ADA) it accumulates in T lymphocytes and kills these cells resulting in a genetic disorder known as adenosine deaminase severe combined immunodeficiency disease ( ADA-SCID). See also *Deoxyribonucleotide * Cordycepin (3′-deoxyadenosine) *Severe combined immunodeficiency Severe combined immunodeficiency (SCID), also known as Swiss-type agammaglobulinemia, is a rare genetic disorder characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations that result in dif ... References Nucleosides Purines Hydroxymethyl compounds {{Cell-biology- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleoside
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar ( ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups. In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or the N1 of a pyrimidine. Nucleotides are the molecular building-blocks of DNA and RNA. List of nucleosides and corresponding nucleobases The reason for 2 symbols, shorter and longer, is that the shorter ones are better for contexts where explicit disambiguation is superfluous (because context disambiguates) and the longer ones are for contexts where explicit disambiguation is judged to be needed or wise. For example, when discussing long nucleobase sequences in genomes, the CATG symbol system is much preferable to the Cyt-Ade-Thy-Gua symbol system (see ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenine
Adenine () (symbol A or Ade) is a nucleobase (a purine derivative). It is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The three others are guanine, cytosine and thymine. Its derivatives have a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD), flavin adenine dinucleotide (FAD) and Coenzyme A. It also has functions in protein synthesis and as a chemical component of DNA and RNA. The shape of adenine is complementary to either thymine in DNA or uracil in RNA. The adjacent image shows pure adenine, as an independent molecule. When connected into DNA, a covalent bond is formed between deoxyribose sugar and the bottom left nitrogen (thereby removing the existing hydrogen atom). The remaining structure is called an ''adenine residue'', as part of a larger molecule. Adenosine is adenine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Adenosine Monophosphate
Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3',5'-cyclic adenosine monophosphate) is a second messenger important in many biological processes. cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway. History Earl Sutherland of Vanderbilt University won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers (such as cyclic adenosine monophosphate, cyclic AMP). Synthesis Cyclic AMP is synthesized from ATP by adenylate cyclase located on the inner side of the plasma membrane and anchored at various locations in the interior of the cell. Adenylate cyclase is ''activated'' by a range of signaling molecules through the activation of adenylate cyclase stimulatory G ( Gs)-protein-coupled receptors. Adenylate cyclase is ''inhibited'' by agonists of adenylate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipyridamole
Dipyridamole (trademarked as Persantine and others) is a nucleoside transport inhibitor and a PDE3 inhibitor medication that inhibits blood clot formation when given chronically and causes blood vessel dilation when given at high doses over a short time. Medical uses * Dipyridamole is used to dilate blood vessels in people with peripheral arterial disease and coronary artery disease * Dipyridamole has been shown to lower pulmonary hypertension without significant drop of systemic blood pressure * It inhibits formation of pro-inflammatory cytokines ( MCP-1, MMP-9) in vitro and results in reduction of hsCRP in patients. * It inhibits proliferation of smooth muscle cells in vivo and modestly increases unassisted patency of synthetic arteriovenous hemodialysis grafts. * It increases the release of tissue plasminogen activator from brain microvascular endothelial cells. * It results in an increase of 13-hydroxyoctadecadienoic acid and decrease of 12-hydroxyeicosatetraenoic ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribose
Ribose is a simple sugar and carbohydrate with molecular formula C5H10O5 and the linear-form composition H−(C=O)−(CHOH)4−H. The naturally-occurring form, , is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes. It has a structural analog, deoxyribose, which is a similarly essential component of DNA. is an unnatural sugar that was first prepared by Emil Fischer and Oscar Piloty in 1891. It was not until 1909 that Phoebus Levene and Walter Jacobs recognised that was a natural product, the enantiomer of Fischer and Piloty's product, and an essential component of nucleic acids. Fischer chose the name "ribose" as it is a partial rearrangement of the name of another sugar, arabinose, of which ribose is an epimer at the 2' carbon; both names also relate to gum arabic, from which arabinose was first isolated and from which they prepared . Like most sugars, ribose exis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AV Nodal Reentrant Tachycardia
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia. It is more common in women than men (approximately 75% of cases occur in females). The main symptom is palpitations. Treatment may be with specific physical maneuvers, medications, or, rarely, synchronized cardioversion. Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed. AVNRT occurs when a reentrant circuit forms within or just next to the atrioventricular node. The circuit usually involves two anatomical pathways: the fast pathway and the slow pathway, which are both in the right atrium. The slow pathway (which is usually targeted for ablation) is located inferior and slightly posterior to the AV node, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical SAM
Radical SAM is a designation for a superfamily of enzymes that use a + cluster">Fe-4Ssup>+ cluster to reductively cleave ''S''-adenosyl-L-methionine (SAM) to generate a radical, usually a 5′- deoxyadenosyl radical (5'-dAdo), as a critical intermediate. These enzymes utilize this radical intermediate to perform diverse transformations, often to functionalize unactivated C-H bonds. Radical SAM enzymes are involved in cofactor biosynthesis, enzyme activation, peptide modification, post-transcriptional and post-translational modifications, metalloprotein cluster formation, tRNA modification, lipid metabolism, biosynthesis of antibiotics and natural products etc. The vast majority of known radical SAM enzymes belong to the radical SAM superfamily, and have a cysteine-rich motif that matches or resembles CxxxCxxC. rSAMs comprise the largest superfamily of metal-containing enzymes. History and mechanism As of 2001, 645 unique radical SAM enzymes have been identified from 126 spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Technetium-99m
Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope in the world. Technetium-99m is used as a radioactive tracer and can be detected in the body by medical equipment ( gamma cameras). It is well suited to the role, because it emits readily detectable gamma rays with a photon energy of 140 keV (these 8.8 pm photons are about the same wavelength as emitted by conventional X-ray diagnostic equipment) and its half-life for gamma emission is 6.0058 hours (meaning 93.7% of it decays to 99Tc in 24 hours). The relatively "short" physical half-life of the isotope and its biological half-life of 1 day (in terms of human activity and metabolism) allows for scanning procedures which collect data rapidly but keep total patient radiation exposure low. The same characteristics ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supraventricular Tachycardia
Supraventricular tachycardia (SVT) is an umbrella term for fast heart rhythms arising from the upper part of the heart. This is in contrast to the other group of fast heart rhythms – ventricular tachycardia, which start within the lower chambers of the heart. There are four main types of SVT: atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and Wolff–Parkinson–White syndrome. The symptoms of SVT include palpitations, feeling of faintness, sweating, shortness of breath, and/or chest pain. These abnormal rhythms start from either the atria or atrioventricular node. They are generally due to one of two mechanisms: re-entry or increased automaticity. Diagnosis is typically by electrocardiogram (ECG), holter monitor, or event monitor. Blood tests may be done to rule out specific underlying causes such as hyperthyroidism or electrolyte abnormalities. A normal resting heart rate is 60 to 100 beats per minute. A resting heart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AV Reentrant Tachycardia
Atrioventricular reentrant tachycardia (AVRT), or atrioventricular reciprocating tachycardia, is a type of abnormal fast heart rhythm and is classified as a type of supraventricular tachycardia (SVT). AVRT is most commonly associated with Wolff–Parkinson–White syndrome, but is also seen in permanent junctional reentrant tachycardia (PJRT). In AVRT, an accessory pathway allows electrical signals from the heart's ventricles to enter the atria and cause earlier than normal contraction, which leads to repeated stimulation of the atrioventricular node.Josephson ME. Preexcitation syndromes. In: Clinical Cardiac Electrophysiology, 4th, Lippincott Williams & Wilkins, Philadelphia 2008. p.339 Signs and symptoms An episode of SVT may present with palpitations, dizziness, shortness of breath, or losing consciousness (fainting). The electrocardiogram (ECG) would appear as a narrow-complex SVT. Between episodes of tachycardia the affected person is likely to be asymptomatic; howeve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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