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Closed-loop therapy
Closed-loop therapy is medical treatment in which a device continuously measures a patient's physiological state and automatically adjusts therapy, as in automated insulin delivery and adaptive neurostimulation.
Closing Volume
Closing volume is the expired lung volume between the onset of small-airway closure in dependent lung zones and residual volume; closing capacity equals closing volume plus residual volume. It rises linearly with age, measured by single-breath nitrogen washout, and exceeds FRC in the elderly.
Closteroviridae
Closteroviridae, closteroviruses: family of plant viruses with very long flexuous filamentous virions (650–2,200 nm) and large 13–19.3 kb positive-sense RNA genomes; hallmark HSP70h and CPm genes; aphid, whitefly, or mealybug transmission.
Clostridiaceae
Clostridiaceae, the Clostridium family, is a family of spore-forming anaerobic Gram-positive bacteria in class Clostridia, order Eubacteriales; type genus Clostridium with type species C. butyricum, including major toxin-producing pathogens.
Clostridioides
Clostridioides is a genus of Gram-positive, spore-forming obligate anaerobes in Peptostreptococcaceae, created in 2016 when Clostridium difficile was reclassified as Clostridioides difficile; type species C. difficile, also C. mangenotii.
Clostridioides difficile
Clostridioides difficile, formerly Clostridium difficile and commonly called C. diff, is a spore-forming bacterium causing diarrhea and colitis, responsible for nearly 500,000 infections a year in the United States.
Clostridioides difficile infection
Clostridioides difficile infection (CDI, C. diff), colitis from the spore-forming bacterium Clostridioides difficile; ~500,000 US cases yearly, triggered by antibiotics, treated with fidaxomicin or vancomycin.
Clostridium
Clostridium, genus of anaerobic spore-forming bacteria (type species C. butyricum); once broadly defined, now restricted; includes C. botulinum, C. perfringens, C. tetani; C. difficile moved to Clostridioides.
Clostridium acetobutylicum
Clostridium acetobutylicum, the Weizmann organism, is a gram-positive anaerobic spore-forming bacterium behind the ABE fermentation producing acetone, butanol, and ethanol; industrial since 1916, model strain ATCC 824, genome sequenced 2001.
Clostridium botulinum
Clostridium botulinum, formerly Bacillus botulinus, is an anaerobic spore-forming Gram-positive rod producing botulinum neurotoxin, one of the most lethal toxins known; it causes botulism and supplies Botox, and taxonomy now splits it among seven clostridial species.
Clostridium butyricum
Clostridium butyricum is an anaerobic, spore-forming gut bacterium first isolated in 1880 that produces butyric acid, with probiotic strains studied for gut disorders, though safety is strain-dependent.
Clostridium perfringens
Clostridium perfringens (formerly C. welchii) is a Gram-positive, spore-forming anaerobic bacterium causing food poisoning, gas gangrene, and animal enterotoxaemia. Strains are toxinotypes A to G defined by alpha, beta, epsilon, iota toxins, CPE, and NetB; CDC estimates nearly 900,000 US foodborne illnesses yearly.
Clostridium tetani
Clostridium tetani, the tetanus bacillus, is a spore-forming gram-positive anaerobe in soil and animal feces whose plasmid-borne tetanospasmin toxin causes tetanus; preventable only by vaccination, not person-to-person spread.
Clot Retraction
Clot retraction (clot contraction): platelet-driven shrinkage of a fibrin blood clot via integrin αIIbβ3 outside-in signaling and the actin-myosin cytoskeleton, expelling serum, stabilizing the clot, and retarding fibrinolysis.
Clothianidin
Clothianidin (TI-435) is a systemic neonicotinoid insecticide developed by Takeda, acting on nicotinic acetylcholine receptors; used as seed treatment and foliar spray, highly toxic to bees, restricted in the EU and Canada.
Clothing fetish
Clothing fetish: sexual arousal centered on garments, fabrics, or footwear rather than the body. A paraphilia described since the 19th century; diagnosable as fetishistic disorder only with distress or impairment, and removed from ICD-11 (2022).
Clotiazepam
Clotiazepam (Rize, Tienor) is a thienodiazepine anxiolytic, CAS 33671-46-4, half-life about 4 hours, 99% protein bound, UN 1971 Convention controlled, Schedule IV in US and Canada, not FDA approved.
Clotrimazole
Clotrimazole (Canesten, Lotrimin) is a topical imidazole antifungal introduced by Bayer in 1969; it inhibits fungal CYP51/ergosterol synthesis and treats skin, oral, vaginal, and ear fungal infections, being less effective than fluconazole for oral candidiasis.
Cloud forest
Cloud forest (tropical montane cloud forest, TMCF): mountain forest regularly immersed in fog, defined by cloud immersion rather than elevation. Covers ~215,000 km2, high endemism, gains water via fog drip, threatened by deforestation and cloud uplift.
Clouded leopard
The clouded leopard (Neofelis nebulosa), also called the mainland clouded leopard, is a medium-sized wild cat of South and Southeast Asian forests, listed as Vulnerable by the IUCN.
Cloven hoof
Cloven hoof: a hoof divided into two parts, characteristic of even-toed artiodactyls (cattle, sheep, goats, pigs, deer) walking on digits III and IV, with dewclaws; contrasted with the horse's single-toed hoof.
Clover
Clover (Trifolium), also called trefoils, is a legume genus of about 240+ species centered in north temperate regions; white clover (T. repens) and red clover (T. pratense) are major forage and nitrogen-fixing pasture plants.
CLOVES syndrome
CLOVES syndrome (CLOVE syndrome, congenital lipomatous overgrowth-vascular malformation-epidermal nevi-skeletal anomaly syndrome) is a rare sporadic PROS overgrowth disorder caused by mosaic PIK3CA mutations, with congenital fatty overgrowth, truncal vascular malformations, epidermal nevi, and spinal anomalies; treated with alpelisib.
Clownfish
Clownfish, also called anemonefish, are small coral reef fish in the Amphiprioninae subfamily. They live in mutualistic symbiosis with sea anemones and are famous for Finding Nemo.
Clozapine
Clozapine (Clozaril, Versacloz) is the first atypical antipsychotic, the standard treatment for treatment-resistant schizophrenia and recurrent suicidality, requiring ANC blood monitoring; its US REMS was eliminated in June 2025.
CLPB
CLPB (SKD3) is the human mitochondrial intermembrane-space AAA+ protein disaggregase with a unique ankyrin-repeat domain; biallelic CLPB mutations cause 3-methylglutaconic aciduria type VII (CLPB deficiency) with neutropenia, cataracts, and neurological disease.
ClpX
ClpX is a hexameric AAA+ ATP-dependent unfoldase that, with the ClpP peptidase, forms the ClpXP protease; it pulls on substrate degron tags, unfolds proteins, and translocates them into ClpP, and also acts alone in protein remodeling.
CLTC
CLTC is the human gene at 17q23 encoding clathrin heavy chain 1 (CHC17), the ubiquitous 1,675-residue heavy chain of clathrin triskelia driving endocytosis and mitosis; pathogenic variants cause MRD56 intellectual disability.
Club cell
Club cell (formerly Clara cell, bronchiolar exocrine cell): non-ciliated secretory epithelial cell of bronchioles expressing SCGB1A1/CCSP (CC10, CC16, uteroglobin); progenitor for airway repair; renamed in 2012-2013 due to Max Clara's Nazi ties.
Club drug
Club drugs, also called party drugs, are psychoactive substances used at nightclubs, raves, and parties, chiefly MDMA, GHB, ketamine, Rohypnol, methamphetamine, and LSD, with risks including overdose and drink-spiking assault.