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DEFB4A
DEFB4A (defensin beta 4A, formerly DEFB2/DEFB4) is a human protein-coding gene at 8p23.1 encoding human beta-defensin 2 (HBD-2, SAP1), an inflammation-inducible, salt-sensitive antimicrobial peptide; closest paralog DEFB4B; linked to psoriasis copy number and UC biomarker studies.
Defecation
Defecation is the expulsion of feces through the anus, coordinated by the enteric, spinal, and central nervous systems, the pelvic floor, and the anal sphincters; most people defecate 1 to 3 times daily.
Defecography
Defecography (evacuation proctography) is real-time fluoroscopic or MRI imaging of defecation to assess pelvic floor disorders such as rectocele, enterocele, intussusception, and dyssynergia.
Defective Viruses
Defective viruses lack a complete genome and cannot fully replicate or form a protein coat without a helper virus. Includes defective interfering particles (DIPs/DVGs), first seen by von Magnus in 1940s influenza, and satellite viruses; they interfere with replication, stimulate immunity, and drive persistence.
Defects of O-glycan initiation and core extension
Defects of O-glycan initiation and core extension are inborn errors of metabolism in which the first sugars attached to a protein's serine or threonine residues cannot be built correctly.
Defence against restriction A, N-terminal
Defence against restriction A, N-terminal: N-terminal region of DarA, a bacteriophage P1 virion protein packaged in the head and coinjected with DNA to protect it from host type I restriction systems, acting strictly in cis.
Defensin-like
Defensin-like (DEFL/DLP) proteins: small cysteine-rich, cationic peptides sharing the defensin fold, split into cis- and trans-defensin superfamilies of independent origin; functions span antimicrobial activity, fertilization signaling, ion channel toxins, and enzyme inhibition.
Defensin-like peptide
Defensin-like peptide (DLP): small disulfide-rich peptides structurally resembling defensins but outside the alpha, beta, and theta subfamilies; prototypes DLP-1 and DLP-2 from platypus venom (PDB 1B8W, 1D6B), InterPro IPR012553, Pfam PF08131; also insect and plant peptides such as DLP4.
Defensin-like protein
Defensin-like proteins (DEFLs, InterPro IPR010851) are plant cysteine-rich proteins resembling defensins; several hundred genes per genome, over 300 in Arabidopsis, with roles in immunity and pollen-pistil signaling.
Defensins
Defensins are small cationic antimicrobial peptides of innate immunity, defined by six cysteines and three disulfide bonds; human alpha- and beta-defensins come from neutrophils, epithelial, and Paneth cells, while theta-defensins are pseudogenes in humans.
Defibrillation
Defibrillation: electric shock treatment terminating ventricular fibrillation or pulseless ventricular tachycardia, via manual defibrillators, public-access AEDs, or implanted cardioverter defibrillators; biphasic waveforms, 150–360 J energies, and bystander AED use doubling or tripling survival distinguish it.
Defibrillators
Defibrillators are devices that send an electric shock to restore normal heart rhythm during cardiac arrest. Covers AEDs for bystanders, manual clinician units, ICDs, hands-off time, usability, and history.
Defibrotide
Defibrotide (Defitelio), a porcine-mucosal-DNA-derived oligonucleotide mixture, is the approved antithrombotic/profibrinolytic drug for hepatic veno-occlusive disease with renal or pulmonary dysfunction after HSCT (US, 2016) and severe VOD/SOS (EU).
Deficiency in anterior pituitary function-variable immunodeficiency syndrome
DAVID syndrome (Deficiency in anterior pituitary function-variable immunodeficiency syndrome, ORPHA:293978) is a rare autosomal dominant NFKB2-related disorder combining childhood-onset common variable immunodeficiency with later ACTH deficiency.
Deficiency of adenosine deaminase 2
Deficiency of adenosine deaminase 2 (DADA2), an autosomal recessive autoinflammatory disease from ADA2 (CECR1) loss-of-function mutations, causing vasculitis, early-onset stroke, bone marrow failure, and immunodeficiency; treated with TNF inhibitors.
Deficit irrigation
Deficit irrigation is an agricultural water management strategy that deliberately gives crops less water than they need, accepting mild stress to maximize yield per unit of water.
DEFINE-FLOW trial
DEFINE-FLOW (NCT02328820), a prospective nonrandomized multicenter trial of 455 patients in Europe and Japan, tested combined FFR and CFR measurement for coronary stenoses; intact CFR did not make low-FFR lesions safe to defer revascularization.
Definitive chemoradiotherapy
Definitive chemoradiotherapy (dCRT) treats localized cancer with concurrent full-dose radiation and chemotherapy, without surgery, aiming at cure; it is best established for locally advanced esophageal cancer.
Definitive fixation
Definitive fixation is the permanent implant-based stabilization of a fracture, recommended as primary treatment in stable patients, while unstable polytrauma patients first receive temporary external fixation.
Definitive radiotherapy
Definitive radiotherapy is radiation treatment given with curative intent as the primary or sole therapy for a tumor, without surgery, typically delivered in small daily doses over several weeks.
Deflazacort
Deflazacort (Emflaza) is a corticosteroid prodrug, FDA-approved in 2017 for Duchenne muscular dystrophy in patients 2 years and older, dosed 0.9 mg/kg/day, metabolized via CYP3A4 to 21-desacetyldeflazacort.
Deforestation
Deforestation is the permanent conversion of forest to other land uses, mainly agriculture, which drives almost 90 percent of it; annual loss fell from 11 to 7.8 million hectares between 2000-2010 and 2010-2018.
Deforestation of the Amazon rainforest
Deforestation of the Amazon rainforest: permanent forest conversion, mainly to cattle pasture and soy, with about 17% of cover lost and 38% of remaining forest degraded; Brazilian annual clearing fell from a 27,772 km² peak in 2004 to 5,731 km² in 2025.
Deformable image registration
Deformable image registration is a medical image processing method that aligns two images of anatomy by locally warping one until its structures match, used most extensively in radiotherapy treatment planning.
Deformed wing virus
Deformed wing virus (DWV), an Iflaviridae RNA virus of honey bees, is vectored by Varroa destructor mites; variants DWV-A and DWV-B (VDV-1) cause deformed wings and colony losses, with DWV-B now displacing DWV-A globally.
DEFUSE 3 trial
DEFUSE 3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3), NINDS-funded StrokeNet randomized trial of thrombectomy 6-16 hours after stroke onset with perfusion-mismatch selection; 182 patients, functional independence 45% vs 17%, extended thrombectomy window to 24 hours with DAWN.
Degarelix
Degarelix (Firmagon, FE200486) is an injectable GnRH antagonist peptide by Ferring for advanced hormone-dependent prostate cancer; 240 mg then 80 mg monthly, rapid castration without flare, main drawback injection-site reactions.
Degenerative disc disease
Degenerative disc disease, also called discogenic disease or intervertebral disc degeneration, is painful breakdown of spinal discs; imaging degeneration is nearly universal with age, definitions vary, and treatment is mostly conservative.
Degenerative disease
A degenerative disease, also called a degenerative disorder, is one marked by progressive deterioration in how affected tissues or organs work; examples include osteoarthritis, osteoporosis, and Alzheimer disease.
Degenerative high myopia
Degenerative high myopia, also called pathologic myopia, is a form of myopia in which excessive elongation of the eyeball causes structural damage that can lead to vision loss.