All articles starting with P
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Polychlorinated dibenzodioxins
Polychlorinated dibenzodioxins (PCDDs), part of the dioxins with PCDFs and dioxin-like PCBs, are 75 congeners of toxic combustion by-products; TCDD is the most toxic, with a 7-11 year body half-life and >90% exposure via food.
Polychlorinated dibenzofurans
Polychlorinated dibenzofurans (PCDFs) are a class of 135 toxic aromatic contaminants, never made intentionally, that form in waste combustion and chemical processes and are grouped with dioxins.
Polychromatophilic erythroblast
Polychromatophilic erythroblast (rubricyte, intermediate normoblast), the third nucleated stage of erythropoiesis: 12–15 µm in humans, gray-lilac cytoplasm from mixed RNA and hemoglobin staining, matures into the orthochromatic erythroblast.
Polychronis C. Tzedakis
Polychronis C. Tzedakis, known as Chronis Tzedakis, is a palaeoclimatologist and palaeoecologist who has been Professor of Physical Geography at University College London since 2009.
Polycladida
Polycladida (polyclads) is an order of free-living marine flatworms with branched intestines, split into Acotylea and Cotylea by the ventral cotyl sucker; roughly 800–1,000 species, with Boniniidae diverging about 550 Mya.
Polyclonal antibodies
Polyclonal antibodies: heterogeneous mixtures of immunoglobulins from many B cell clones binding multiple epitopes, raised in immunized animals; cheaper and faster than monoclonals, batch-variable, and the basis of antivenoms.
Polyclonal hypergammaglobulinaemia
Polyclonal hypergammaglobulinaemia, or polyclonal gammopathy (ICD-11 4B21), is a reactive rise in immunoglobulins from many plasma cell clones, seen as a broad gamma band on electrophoresis, caused mainly by liver disease, autoimmunity, infection, and IgG4-related disease.
Polyclonal hyperviscosity syndrome
Polyclonal hyperviscosity syndrome, a rare hematologic disorder (ORPHA 450322, ICD-10 D89.0) in which polyclonal immunoglobulin expansion raises serum viscosity, causing bleeding, retinal hemorrhage, and neurologic symptoms; linked to Sjögren, rheumatoid arthritis, HIV, and IgG4-related disease.
Polycom
Polycom, Inc. was an American communications equipment company founded in 1990, best known for the SoundStation conference phone and videoconferencing systems; Plantronics acquired it in 2018.
Polycomb recruitment in X chromosome inactivation
Polycomb recruitment in X chromosome inactivation: Xist RNA B-repeat binds hnRNPK, recruiting PCGF3/5-PRC1, whose H2AK119ub recruits PRC2, depositing H3K27me3 on the inactive X.
Polycomb-group proteins
Polycomb-group (PcG) proteins are conserved chromatin regulators, organized into PRC1 and PRC2, that repress HOX and developmental genes via H2AK119ub1 and H3K27me3; deregulation links to cancer.
Polycondensation
Polycondensation is a polymerization in which polymer chains grow through condensation reactions that expel a small molecule such as water, producing polyesters, polyamides, and other industrial and natural polymers.
Polycrisis
Polycrisis is a term for several distinct global crises interacting to produce harms greater than the sum of their separate parts, coined by Edgar Morin in 1993.
Polycrystalline diamond
Polycrystalline diamond (PCD) is a synthetic engineering material of diamond particles sintered into a coherent solid, often with a cobalt binder, used mainly for cutting tools, drill bits, and wear parts.
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is high-purity silicon of many small crystals joined by grain boundaries, made by the Siemens process as feedstock for solar wafers and chips.
Polycrystalline SnSe thermoelectric
Polycrystalline tin selenide (SnSe) is a bulk, multi-grain form of the layered semiconductor SnSe, a thermoelectric material that converts heat into electricity and is cheaper and more scalable to make than single crystals.
Polycube
A polycube is a solid figure formed by joining unit cubes face to face, the three-dimensional generalization of the two-dimensional polyomino, introduced by Martin Gardner in 1969.
Polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbons, also known as PAHs, are organic compounds made of fused benzene rings, formed by incomplete combustion; more than 100 exist, many toxic and carcinogenic.
Polycystic kidney disease
Polycystic kidney disease (PKD) is a genetic disorder in which numerous fluid-filled cysts grow in the kidneys, enlarging them, reducing function, and often leading to kidney failure.
Polycystic ovary syndrome
Polycystic ovary syndrome (PCOS), also known as polyendocrine metabolic ovarian syndrome (PMOS) and formerly Stein-Leventhal syndrome, is a hormonal disorder of women, marked by excess androgens, irregular periods, and infertility.
Polycystin 1
Polycystin 1 (PC1) is a large membrane protein encoded by the PKD1 gene that forms a ciliary complex with polycystin 2, and whose loss causes most cases of autosomal dominant polycystic kidney disease.
Polycystin 2
Polycystin 2 (PC2, TRPP2, PKD2) is a TRP-family calcium-permeable nonselective cation channel encoded by PKD2, found on the ER, primary cilium, and plasma membrane; PKD2 mutations cause ADPKD, a milder form than PKD1.
Polycystin cation channel family
Polycystin cation channel family: eight TRP-related proteins (PKD1-related, PKD2-related) forming homo- and heterotetrameric cation channels in cilia and ER; PC1–PC2 1:3 complex mutated in ADPKD.
Polycystinea
Polycystinea (Polycystina) is a class of siliceous-shelled radiolarian protists in Rhizaria, with orders Spumellaria, Nassellaria, Collodaria, and Entactinaria, a Cambrian-to-present fossil record, about 600 living species, and major use in biostratigraphy and paleoceanography.
Polycythemia
Polycythemia (erythrocytosis): raised red blood cell count, either absolute (increased red cell mass, e.g. JAK2-mutated polycythemia vera) or relative (hemoconcentration). Diagnosed by sex-specific hemoglobin/hematocrit thresholds, JAK2 testing, and EPO levels; managed with phlebotomy to hematocrit below 45%, aspirin, and cytoreduction.
Polycythemia vera
Polycythemia vera, also known as Osler-Vaquez disease, is a blood cancer in which the bone marrow makes too many red blood cells, raising the risk of blood clots.
Polydactyl cat
Polydactyl cat (Hemingway cat): a domestic cat born with extra toes, usually on the front paws, caused by autosomal dominant ZRS/LMBR1 variants affecting SHH; main care need is regular nail trimming.
Polydactyly
Polydactyly (supernumerary digits, extra fingers or toes) is a congenital anomaly affecting about 2 per 1,000 births, caused by GLI3 or SHH enhancer ZRS mutations, occurring isolated or syndromic, and treated by ligation or surgical excision.
Polydactyly of a biphalangeal thumb and/or hallux
Polydactyly of a biphalangeal thumb and/or hallux (PPD1, MIM 174400, ORPHA 93339) is a rare non-syndromic malformation duplicating a two-phalanx thumb or great toe, right-sided, linked to GLI1 on 7q36.
Polydactyly of a triphalangeal thumb
Polydactyly of a triphalangeal thumb (PPD2, preaxial polydactyly type II, OMIM 174500) is a rare autosomal dominant limb malformation: a three-phalanx, usually opposable thumb, caused by ZRS/SHH enhancer mutations, linked to Holt-Oram and Fanconi anemia.