Life and health

Hirudin Therapy

Hirudin therapy: anticoagulant treatment using hirudins, direct thrombin inhibitors from medicinal leech saliva (lepirudin, desirudin, bivalirudin), used mainly for heparin-induced thrombocytopenia and PCI, distinct from heparin by clot-bound thrombin inhibition.

Hirudo medicinalis

Hirudo medicinalis, the European medicinal leech, is a freshwater bloodsucking annelid described by Linnaeus in 1758, source of hirudin, CITES Appendix II, and now distinguished from the commercially supplied Hirudo verbana.

Hirudo verbana

Hirudo verbana (southern or Hungarian medicinal leech, Carena 1820) is a European freshwater blood-feeding leech from Switzerland and Italy to Turkey and Uzbekistan; the most commercially supplied medicinal leech, long mislabeled as H. medicinalis, CITES Appendix II listed, Vulnerable in Romania.

Hirudotherapy

Hirudotherapy is the controlled medicinal use of leeches, chiefly to relieve venous congestion after reconstructive surgery; in the United States, medicinal leeches are FDA-cleared medical devices.

Hirundo

Hirundo (Linnaeus, 1758) is the barn swallow genus of the swallow family Hirundinidae, order Passeriformes; type species Hirundo rustica, about 14-16 cosmopolitan species, mud-nesting aerial insectivores with four well-supported phylogenetic clades.

His bundle tachycardia

His bundle tachycardia, or junctional ectopic tachycardia (JET), is a rare arrhythmia of increased AV node and His bundle excitability in newborns, showing AV dissociation, narrow QRS, and sinus capture beats (ORPHA:3283).

Hisamaru Hirai

Hisamaru Hirai (平井久丸, 1952–2003) was a Japanese hematologist and oncologist, professor at the University of Tokyo, known for work on the molecular genetics of leukemia and MDS.

Hisao Masai

Hisao Masai (正井久雄) is a Japanese molecular biologist known for research on DNA replication and, since 2018, Director General of Tokyo Metropolitan Institute of Medical Science.

Hisao Masukata

Hisao Masukata (升方久夫) is a Japanese molecular biologist and professor at Osaka University whose research established how DNA replication initiates in the ColE1 plasmid and fission yeast.

Hisao Ogawa

Hisao Ogawa (小川久雄, born 1953) is a Japanese cardiologist who became the 14th president of Kumamoto University in 2021, after leading the National Cerebral and Cardiovascular Center.

Hisashi Arase

Hisashi Arase (荒瀬尚) is a Japanese immunologist and professor at the University of Osaka known for work on autoimmunity, immune regulation, and host-pathogen interactions.

Hisashi Umemori

Hisashi Umemori is a neuroscientist and physician, Professor of Neurology at Harvard Medical School, known for identifying FGF22 as a target-derived signal that organizes synapse formation.

Hisataka Kobayashi

Hisataka Kobayashi (小林久隆) is a Japanese-born physician-scientist and Senior Investigator at the National Cancer Institute in Bethesda, Maryland, known for developing near-infrared photoimmunotherapy, approved in Japan in 2020.

Hisham Mehanna

Hisham Mehanna (Hisham Mohamed Mehanna) is a British head and neck surgeon, Professor at the University of Birmingham, known for the PET-NECK and De-ESCALaTE HPV trials.

Histamine H1 receptor

Histamine H1 receptor (HRH1), a Gq-coupled GPCR on chromosome 3p14-p21 mediating allergy symptoms; target of first- and second-generation H1 antihistamines, which act as inverse agonists.

Histamine H2 receptor

Histamine H2 receptor (HRH2, P25021), a Gs-coupled GPCR mediating gastric acid secretion; defined by burimamide in 1972, cloned 1991, target of cimetidine (Tagamet) and other H2 blockers; cryo-EM structures solved 2024.

Histamine H3 receptor

Histamine H3 receptor (H3R): a Gi/o-coupled GPCR, discovered in 1983 and cloned in 1999, acting mainly as a presynaptic autoreceptor inhibiting histamine release; pitolisant (Wakix) is its approved antagonist/inverse agonist drug for narcolepsy.

Histamine H4 receptor

Histamine H4 receptor (H4R, HRH4): fourth histamine GPCR, discovered circa 2000 via H3 homology, expressed mainly on immune cells, mediates chemotaxis; antagonists JNJ 7777120, JNJ 39758979, and toreforant reached clinical testing but none is approved.

Histamine intolerance

Histamine intolerance (HIT), or sensitivity to dietary histamine, is a proposed nonallergic food hypersensitivity attributed to impaired diamine oxidase (DAO) degradation of ingested histamine; diagnosis is unvalidated, serum DAO is contested, and a low-histamine diet is the mainstay treatment.

Histamine N-methyltransferase

Histamine N-methyltransferase (HNMT; EC 2.1.1.8) is a cytosolic enzyme that inactivates histamine by transferring a methyl group to it, one of the body's two histamine-clearing pathways.

Histamine receptors

Histamine receptors: four human G protein-coupled receptors, H1-H4, mediating histamine's effects in allergy, gastric acid secretion, and neurotransmission; H1 and H2 are established drug targets, pitolisant targets H3.

Histamine Release

Histamine release: rapid discharge of histamine from mast cell and basophil granules, typically triggered by antigen cross-linking surface IgE on FcεRI; measured historically by the histamine release test, now largely supplanted by the basophil activation test.

Histaminergic neuron

Histaminergic neurons, the brain's only histamine-releasing neurons, sit in the tuberomammillary nucleus of the posterior hypothalamus, fire as wake-promoting pacemakers, project throughout the CNS, and signal via H1–H4 receptors.

Histatin/statherin family

The histatin/statherin family is a group of small human salivary peptides, including the histatins and statherin, whose genes arose by duplication and which remineralize tooth enamel and defend against Candida albicans.

Histeridae

Histeridae, clown beetles or hister beetles, is a family of over 4800 predatory beetle species under 10 mm long, living in dung, carrion, and wood-boring galleries, with retractable antennae and uses in biological control and forensics.

Histidine ammonia-lyase

Histidine ammonia-lyase (HAL, histidase, EC 4.3.1.3) catalyzes the first step of histidine catabolism, deaminating L-histidine to trans-urocanic acid using an autocatalytic MIO prosthetic group; deficiency causes histidinemia.

Histidine catabolism

Histidine catabolism is the biochemical breakdown of the essential amino acid L-histidine to glutamate via a four-step cytosolic pathway that donates a one-carbon unit to tetrahydrofolate.

Histidine kinase

Histidine kinase (HK, histidine protein kinase): enzyme that autophosphorylates on a conserved histidine and transfers phosphate to a response regulator aspartate in two-component signaling; absent from animals, dominant in bacteria, phosphorelay-based in eukaryotes.

Histidine kinase domain

The histidine kinase domain is the conserved catalytic core of histidine kinases in two-component systems, the principal signaling mechanism in bacteria, and a promising antibacterial drug target.