All articles starting with H
20,046 articles
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.
Histidine operon leader peptide
Histidine operon leader peptide (HisL): 16-amino-acid bacterial leader peptide with seven consecutive histidine codons that senses charged tRNA^His in attenuation control of the his biosynthesis operon in E. coli and Salmonella.
Histidine phosphatase superfamily, clade-1
Histidine phosphatase superfamily, clade-1 is the larger of two main branches of a superfamily whose enzymes act through a transiently phosphorylated active-site histidine, spanning bacteria and eukaryotes and including phosphoglycerate mutase and fructose-2,6-bisphosphatase.
Histidinemia
Histidinemia (histidase deficiency, HAL deficiency) is a benign autosomal recessive metabolic disorder with elevated histidine in blood, urine, and CSF, caused by HAL gene mutations at 12q22-q24.1.
Histidinol dehydrogenase
Histidinol dehydrogenase (HisD, HDH, EC 1.1.1.23) is a homodimeric zinc metalloenzyme, encoded by hisD, that catalyzes the final two NAD+-dependent steps of histidine biosynthesis, oxidizing L-histidinol via histidinal to L-histidine in bacteria, archaea, fungi, and plants.
Histidinol-phosphate aminotransferase family
Histidinol-phosphate aminotransferase family (IPR005861): PLP-dependent HisC enzymes, EC 2.6.1.9, catalyzing step 7 of histidine biosynthesis in bacteria, archaea, lower eukaryotes, and plants, absent in mammals.
Histiocytic sarcoma
Histiocytic sarcoma, also called malignant histiocytosis, is an ultra-rare aggressive hematopoietic cancer of mature histiocytes, mostly extranodal, with RAS/MAPK mutations, median survival about six months, and treatment by surgery for localized disease.
Histiocytoid cardiomyopathy
Histiocytoid cardiomyopathy (infantile xanthomatous or oncocytic cardiomyopathy) is a rare mitochondrial arrhythmogenic disorder of infants under 2, mostly girls, causing incessant ventricular tachycardia, sudden death, and mitochondria-rich histiocytoid myocardial cells.
Histiocytoma (dog)
Canine cutaneous histiocytoma, a common benign skin tumor of young dogs arising from epidermal Langerhans cells, expressing E-cadherin, CD18, and MHCII, that usually regresses spontaneously within 2 to 3 months without treatment.
Histiopteris incisa
Histiopteris incisa (Thunb.) J.Sm., the bat's wing fern or water fern (mātā), is a widespread Dennstaedtiaceae fern of the tropics and subtropics, with 1–2 m pale green fronds, marginal continuous sori, and Least Concern to Critically Endangered regional statuses.
Histiotus
Histiotus, or big-eared brown bats, is a genus of insectivorous vesper bats endemic to South America, recognized by very long ears and including 11 species.
Histoblast
Histoblasts are diploid imaginal progenitor cells of Drosophila and other flies, arranged in four pairs of abdominal histoblast nests, that proliferate during pupal metamorphosis to replace larval epidermis and form the adult abdomen.
Histocompatibility testing
Histocompatibility testing is the set of laboratory methods used before transplantation to judge donor-recipient HLA compatibility, informing organ allocation and assessing the risk of rejection.
Histocytochemistry
Histocytochemistry (cytochemistry) is the study of intracellular distribution of chemicals, reaction sites, and enzymes via staining, isotope uptake, and electron microscopy; immunohistochemistry, PAS, and Prussian blue are its MeSH subfields.
Histocytological Preparation Techniques
Histocytological preparation techniques (MeSH D016591) are methods for preparing cells and tissues for microscopy: fixation, paraffin embedding, microtomy, staining, and cell blocks, from specimen handling to FFPE and frozen sections.
Histogram
A histogram is a graphical summary of a single quantitative variable's distribution: the data range is split into intervals called bins, with each bin's count shown as a bar.
Histogram equalization
Histogram equalization is an image-processing transform that increases contrast by remapping pixel intensities through the cumulative distribution function, spreading them over the full intensity range.
Histogram matching
Histogram matching, also called histogram specification, is an image processing technique that remaps pixel intensities so an image's histogram approximates a chosen target, generalizing histogram equalization.
Histogram of oriented gradients
The histogram of oriented gradients (HOG) is a feature descriptor in computer vision, introduced by Navneet Dalal and Bill Triggs in 2005 for detecting people in images.
Histoire ancienne jusqu'à César
Histoire ancienne jusqu'à César, also known as the Estoires Rogier, is a French universal chronicle composed in Flanders around 1208 to 1213 for Roger IV, châtelain of Lille.
Histological Techniques
Histological techniques: methods of preparing tissue (fixation, embedding, sectioning, staining) for microscopic study of structure and pathology; MeSH D006652; H&E standard, IHC from the 1980s.
Histology
Histology, also called microscopic anatomy, is the microscopic study of the structure of biological tissues, prepared by sectioning and staining; in medicine it underlies diagnosis, autopsy, and forensic investigation.
Histology Shadowing Technique
Histology shadowing technique (metal shadowing, shadow casting): TEM specimen preparation evaporating heavy metal such as platinum at an oblique angle, creating shadow contrast and 3D appearance; unidirectional and rotary variants, ~3 nm resolution.
Histomorphometry
Histomorphometry is the quantitative measurement of tissue structure in histological sections, producing counts, areas, and distances; its flagship application, bone histomorphometry, is the gold standard for renal osteodystrophy.
Histone
Histone: small basic eukaryotic proteins (H2A, H2B, H3, H4 core plus H1 linker) that package DNA into nucleosomes of about 147 base pairs and regulate gene expression through variants, chaperones, and post-translational modifications.
Histone acetylation and deacetylation
Histone acetylation and deacetylation: opposing lysine modifications of histones by HATs (acetyl-CoA-dependent) and HDACs (Zn2+- or NAD+-dependent sirtuins) that regulate chromatin and gene expression; also HDAC inhibitor drugs like vorinostat.
Histone acetyltransferase GCN5
KAT2A, also called GCN5, is a GNAT-family lysine acetyltransferase and the catalytic KAT of SAGA and ATAC complexes, acetylating H3K9/H3K14 and acting as a histone succinyltransferase linked to cancer and HBV.
Histone acetyltransferases subunit 3
Histone acetyltransferases subunit 3, or ADA3 (alteration/deficiency in activation 3), is a conserved non-catalytic subunit of GCN5-containing HAT complexes (ADA, SAGA, ATAC, STAGA, TFTC) required for nucleosomal acetylation, p53 acetylation, cell cycle control, and genome stability.
Histone deacetylase
Histone deacetylases (HDACs), also called lysine deacetylases, are 18 human enzymes in four classes (zinc-dependent classes I, II, IV; NAD+-dependent sirtuins, class III) that remove acetyl groups from histone and nonhistone proteins; their inhibitors, such as vorinostat and romidepsin, are approved anticancer drugs.
Histone deacetylase inhibitor
Histone deacetylase (HDAC) inhibitors are epigenetic drugs that block zinc-dependent HDAC enzymes, increasing histone acetylation; four (vorinostat, belinostat, romidepsin, panobinostat) are FDA-approved mainly for lymphoma and myeloma.