All articles starting with H
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Heme
Heme (protoheme IX, Fe-protoporphyrin IX) is an iron-porphyrin cofactor of hemoglobin, cytochromes, and P450 enzymes; ferrous form is heme, ferric form is hemin, with types a, b, c, d, and o.
Heme biosynthesis
Heme biosynthesis, the eight-step pathway producing heme (protoheme IX) from glycine, succinyl-CoA, and iron across mitochondria and cytosol; includes classical PPD route plus CPD and AHB alternatives; defects cause porphyrias.
Heme degradation
Heme degradation is the two-step catabolism of heme by heme oxygenase and biliverdin reductase to bilirubin, carbon monoxide, and iron; humans degrade about 300 mg heme daily, mostly from hemoglobin.
Heme oxygenase
Heme oxygenase (HO, EC 1.14.14.18), also called haem oxygenase, is the rate-limiting enzyme degrading heme into biliverdin, carbon monoxide, and free iron. Isoforms HO-1 (inducible, HSP32) and HO-2 (constitutive) protect cells from oxidative stress.
Heme oxygenase-1 deficiency
Heme oxygenase-1 deficiency (HMOX1D, HO-1 deficiency) is a rare autosomal recessive HMOX1 disorder with asplenia, hemolytic anemia, low bilirubin, hyperinflammation, nephritis, and endothelial injury; first reported 1999.
Hemel Hempstead
Hemel Hempstead: Hertfordshire market town designated a 1947 Mark One New Town, planned by Geoffrey Jellicoe as a town in a park; 60,000 planned population, Water Gardens, Maylands Business Park, and Garden Town growth since 2019.
Hemendra Kumar Roy
Hemendra Kumar Roy (হেমেন্দ্রকুমার রায়), born Prasaddas Ray (1888–1963), was a Bengali writer from Calcutta who pioneered children's adventure, detective, and science fiction, creating Jayanta-Manik and Bimal-Kumar and the classic Jokher Dhan.
Hemera (μέρα)
Hemera (Ἡμέρα), Roman Dies, is the Greek primordial goddess of day, daughter of Nyx and Erebus, sister and wife of Aether in Hesiod's Theogony; later conflated with Eos, with almost no cult or independent myths.
Hemera Dorsa
Hemera Dorsa, also called feature 2444, is a 587-km dorsum (ridge belt) on Venus at 51.0N 243.4E, IAU-approved in 1985 and named for the Greek goddess personifying day.
Hemerobiidae
Hemerobiidae, brown lacewings (Latreille, 1802), a Neuroptera family of small predatory insects; about 560-591 species, forewings 4-12 mm, multiple radial veins from R1, all continents except Antarctica.
Hemesh Singh
Hemesh Singh is an Indian technology entrepreneur who co-founded the Bengaluru ed-tech company Unacademy in 2015 with Gaurav Munjal and Roman Saini, serving as its chief technology officer until 2024.
Hemet, California
Hemet is a city in Riverside County's San Jacinto Valley, incorporated in 1910, with a 2020 population of 89,833 and home of the Ramona Pageant.
Hemet, or the Landlady Don't Drink Tea
Hemet, or the Landlady Don't Drink Tea (also Hemet) is a 2024 American satirical dark comedy horror film directed by Tony Olmos, written by and starring Brian Patrick Butler as landlady Liz Topham-Myrtle, set during a bath-salt zombie epidemic in Hemet, California.
Hemetre
Hemetre is an ancient Egyptian royal woman of Dynasty 4, probably a daughter of King Khafre, known from mastaba G 8464 in the Central Field at Giza, excavated by Selim Hassan.
Hemhem crown
Hemhem crown (hmhm, 'cry out'): ancient Egyptian triple-atef solar headdress with ram's horns, sun disks, plumes and uraei, worn tilted on the nemes by pharaohs, Kushite royalty, and divine children like Harpokrates.
Hemiacetal
A hemiacetal is a functional group in which one carbon bears both a hydroxyl and an alkoxy group, formed when an alcohol adds to an aldehyde; ketone-derived analogs are hemiketals.
Hemianopsia
Hemianopsia is the loss of one half of the vertical visual field, usually caused by stroke, brain tumor, or traumatic brain injury, occurring in homonymous or heteronymous forms depending on where the visual pathways are damaged.
Hemiarthroplasty
Hemiarthroplasty is a hip operation that replaces the femoral head and neck with a prosthesis while leaving the socket untouched, used mainly for displaced femoral neck fractures in older adults.
Hemiazygos vein
The hemiazygos vein, also called the inferior hemiazygos vein, is an unpaired left-sided chest vein that drains the lower posterior chest and abdominal wall and empties into the azygos vein.
Hemibagrus nemurus
Hemibagrus nemurus, the Asian redtail catfish or baung (Bagrus nemurus, Mystus nemurus), is a large bagrid river catfish of the Mekong, Chao Phraya, Malay Peninsula, Sumatra, Java, and Borneo, reaching 65 cm, farmed commercially, IUCN Least Concern.
Hemiballism
Hemiballism (hemiballismus), the most severe form of chorea, causes violent one-sided flinging limb movements from contralateral basal ganglia lesions, classically the subthalamic nucleus though most lesions lie elsewhere; stroke and nonketotic hyperglycemia are leading causes.
Hemibody Irradiation
Hemibody irradiation (HBI), or half-body irradiation, is palliative radiotherapy treating half the body in one field for widespread bone metastases; standard 800 cGy lower and 600 cGy upper doses, about 80% pain response, largely abandoned after the 1990s.
Hemic neoplasia of bivalves
Hemic neoplasia, also called disseminated neoplasia, is a leukemia-like transmissible cancer of marine bivalves, spreading as living cancer cells through seawater and affecting at least 15 species worldwide.
Hemicellulose
Hemicellulose is a group of branched, non-cellulosic polysaccharides in plant cell walls that bind to cellulose and reinforce it, making up 20 to 35% of the wall and including xylans and xyloglucans.
Hemicholinium-3
Hemicholinium-3 (HC-3) is a synthetic bis-quaternary ammonium compound that inhibits the high-affinity choline transporter, blocking acetylcholine synthesis; discovered in 1954, it is a research tool, not a drug.
Hemichordate
Hemichordata, a phylum of marine deuterostomes with two classes, Enteropneusta (acorn worms) and Pterobranchia, about 130 described species, sister to Echinodermata in Ambulacraria, tripartite proboscis-collar-trunk body with gill slits.
Hemichorea
Hemichorea, also called hemichorea-hemiballismus, is unilateral chorea on one side of the body, classically linked to contralateral subthalamic nucleus lesions but usually caused by stroke or non-ketotic hyperglycemia.
Hemichorea or hemiballismus
Hemichorea or hemiballismus (hemichorea-hemiballism, HCHB), ICD-11 8A01.2: unilateral involuntary choreic or flinging proximal movements from contralateral basal ganglia or subthalamic lesions, most often stroke or nonketotic hyperglycemia; treated with neuroleptics, tetrabenazine, or GPi-DBS.
Hemicolectomy
A hemicolectomy is an operation in which a segment of the colon is removed, most often to treat colon cancer, together with the mesentery and lymph nodes that drain it.
Hemiconvulsion-hemiplegia-epilepsy syndrome
Hemiconvulsion-hemiplegia-epilepsy syndrome (HHE, hemiplegia-hemiconvulsion-epilepsy syndrome) is a rare childhood epilepsy syndrome: febrile hemiclonic status epilepticus, immediate permanent hemiplegia, then drug-resistant focal epilepsy within about 3 years.