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VIPR1
Vasoactive intestinal polypeptide receptor 1 also known as VPAC1, is a protein, that in humans is encoded by the ''VIPR1'' gene. VPAC1 is expressed in the brain ( cerebral cortex, hippocampus, amygdala), lung, prostate, peripheral blood leukocytes, liver, small intestine, heart, spleen, placenta, kidney, thymus and testis. Function VPAC1 is a receptor for vasoactive intestinal peptide (VIP), a small neuropeptide. Vasoactive intestinal peptide is involved in smooth muscle relaxation, exocrine and endocrine secretion, and water and ion flux in lung and intestinal epithelia. Its actions are effected through integral membrane receptors associated with a guanine nucleotide binding protein which activates adenylate cyclase. VIP acts in an autocrine fashion via VPAC11 to inhibit megakaryocyte proliferation and induce proplatelet formation. Clinical significance Patients with idiopathic achalasia show a significant difference in the distribution of SNPs aff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vasoactive Intestinal Peptide
Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a peptide of 28 amino acid residues that belongs to a glucagon/secretin superfamily, the ligand of class II G protein–coupled receptors. VIP is produced in many tissues of vertebrates including the gut, pancreas, and suprachiasmatic nuclei of the hypothalamus in the brain. VIP stimulates contractility in the heart, causes vasodilation, increases glycogenolysis, lowers arterial blood pressure and relaxes the smooth muscle of trachea, stomach and gallbladder. In humans, the vasoactive intestinal peptide is encoded by the ''VIP'' gene. VIP has a half-life (t½) in the blood of about two minutes. Function In the body VIP has an effect on several tissues: In the digestive system, VIP seems to induce smooth muscle relaxation ( lower esophageal sphincter, stomach, gallbladder), stimulate secretion of water into pancreatic jui ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuropeptide
Neuropeptides are chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors (GPCRs) to modulate neural activity and other tissues like the gut, muscles, and heart. There are over 100 known neuropeptides, representing the largest and most diverse class of signaling molecules in the nervous system. Neuropeptides are synthesized from large precursor proteins which are cleaved and post-translationally processed then packaged into dense core vesicles. Neuropeptides are often co-released with other neuropeptides and neurotransmitters in a single neuron, yielding a multitude of effects. Once released, neuropeptides can diffuse widely to affect a broad range of targets. Synthesis Neuropeptides are synthesized from large, inactive precursor proteins called prepropeptides. Prepropeptides contain sequences for a family of distinct peptides and often contain repeated copies of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-nucleotide Polymorphism
In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently large fraction of the population (e.g. 1% or more), many publications do not apply such a frequency threshold. For example, at a specific base position in the human genome, the G nucleotide may appear in most individuals, but in a minority of individuals, the position is occupied by an A. This means that there is a SNP at this specific position, and the two possible nucleotide variations – G or A – are said to be the alleles for this specific position. SNPs pinpoint differences in our susceptibility to a wide range of diseases, for example age-related macular degeneration (a common SNP in the CFH gene is associated with increased risk of the disease) or nonalcoholic fatty liver disease (a SNP in the PNPLA3 gene is associated with incr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achalasia
Esophageal achalasia, often referred to simply as achalasia, is a failure of smooth muscle fibers to relax, which can cause the lower esophageal sphincter to remain closed. Without a modifier, "achalasia" usually refers to achalasia of the esophagus. Achalasia can happen at various points along the gastrointestinal tract; achalasia of the rectum, for instance, may occur in Hirschsprung's disease. The lower esophageal sphincter is a muscle between the esophagus and stomach that opens when food comes in. It closes to avoid stomach acids from coming back up. A fully understood cause to the disease is unknown, as are factors that increase the risk of its appearance. Suggestions of a genetically transmittable form of achalasia exist, but this is neither fully understood, nor agreed upon. Esophageal achalasia is an esophageal motility disorder involving the smooth muscle layer of the esophagus and the lower esophageal sphincter (LES). It is characterized by incomplete LES relaxa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Idiopathic
An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. From Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approximately "a disease of its own kind". For some medical conditions, one or more causes are somewhat understood, but in a certain percentage of people with the condition, the cause may not be readily apparent or characterized. In these cases, the origin of the condition is said to be idiopathic. With some other medical conditions, the root cause for a large percentage of all cases have not been established—for example, focal segmental glomerulosclerosis or ankylosing spondylitis; the majority of these cases are deemed idiopathic. Medical advances and this term Advances in medical science improve the understanding of causes of diseases and the classification of diseases; thus, regarding any particular condition or disease, as more root causes are discovered and as events t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megakaryocyte
A megakaryocyte (''mega-'' + '' karyo-'' + '' -cyte'', "large-nucleus cell") is a large bone marrow cell with a lobated nucleus responsible for the production of blood thrombocytes (platelets), which are necessary for normal blood clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte. Structure In general, megakaryocytes are 10 to 15 times larger than a typical red blood cell, averaging 50–100 μm in diameter. During its maturation, the megakaryocyte grows in size and replicates its DNA without cytokinesis in a process called endomitosis. As a result, the nucleus of the megakaryocyte can become very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei. In some cases, the nucleus may contain up t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autocrine
Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on that same cell, leading to changes in the cell. This can be contrasted with paracrine signaling, intracrine signaling, or classical endocrine signaling. Examples An example of an autocrine agent is the cytokine interleukin-1 in monocytes. When interleukin-1 is produced in response to external stimuli, it can bind to cell-surface receptors on the same cell that produced it. Another example occurs in activated T cell lymphocytes, i.e., when a T cell is induced to mature by binding to a peptide: MHC complex on a professional antigen-presenting cell and by the B7:CD28 costimulatory signal. Upon activation, "low-affinity" IL-2 receptors are replaced by "high-affinity" IL-2 receptors consisting of α, β, and γ chains. The cell then releases IL-2, which binds to its own new IL-2 receptors, causing self-stimula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenylate Cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction: :ATP = 3′,5′-cyclic AMP + diphosphate It has key regulatory roles in essentially all cells. It is the most polyphyletic known enzyme: six distinct classes have been described, all catalyzing the same reaction but representing unrelated gene families with no known sequence or structural homology. The best known class of adenylyl cyclases is class III or AC-III (Roman numerals are used for classes). AC-III occurs widely in eukaryotes and has important roles in many human tissues. All classes of adenylyl cyclase catalyse the conversion of adenosine triphosphate (ATP) to 3',5'-cyclic AMP (cAMP) and pyrophosphate.Magnesium ions are generally required and appear to be closely involved in the enzymatic mechanism. The cAMP produced by A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guanine
Guanine () (symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is called guanosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine- imidazole ring system with conjugated double bonds. This unsaturated arrangement means the bicyclic molecule is planar. Properties Guanine, along with adenine and cytosine, is present in both DNA and RNA, whereas thymine is usually seen only in DNA, and uracil only in RNA. Guanine has two tautomeric forms, the major keto form (see figures) and rare enol form. It binds to cytosine through three hydrogen bonds. In cytosine, the amino group acts as the hydrogen bond donor and the C-2 carbonyl and the N-3 amine as the hydrogen-bond acceptors. Guanine has the C-6 carbonyl group that acts as the hydrogen bond acceptor, while a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Receptor
Cell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integral membrane proteins that allow communication between the cell and the extracellular space. The extracellular molecules may be hormones, neurotransmitters, cytokines, growth factors, cell adhesion molecules, or nutrients; they react with the receptor to induce changes in the metabolism and activity of a cell. In the process of signal transduction, ligand binding affects a cascading chemical change through the cell membrane. Structure and mechanism Many membrane receptors are transmembrane proteins. There are various kinds, including glycoproteins and lipoproteins. Hundreds of different receptors are known and many more have yet to be studied. Transmembrane receptors are typically classified based on their tertiary (three-dimen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epithelia
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellular matrix. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the epidermis, the outermost layer of the skin. There are three principal shapes of epithelial cell: squamous (scaly), columnar, and cuboidal. These can be arranged in a singular layer of cells as simple epithelium, either squamous, columnar, or cuboidal, or in layers of two or more cells deep as stratified (layered), or ''compound'', either squamous, columnar or cuboidal. In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei. This sort of tissue is called pseudostratified. All glands are made up of epitheli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
