612 Results for: "western blot detection systems"

Supplier: Prosci

L-glutamate is the major excitatory neurotransmitter in the central nervous system and activates both ionotropic and metabotropic glutamate receptors. The metabotropic glutamate receptors are a family of G protein-coupled receptors, that have been divided into 3 groups on the basis of sequence homology, putative signal transduction mechanisms, and pharmacologic properties. GRM6 is part of Group III which is linked to the inhibition of the cyclic AMP cascade.

Supplier: Prosci

SSB is involved in diverse aspects of RNA metabolism, including binding and protecting 3-prime UUU (OH) elements of newly RNA polymerase III-transcribed RNA, processing 5-prime and 3-prime ends of pre-tRNA precursors, acting as an RNA chaperone, and binding viral RNAs associated with hepatitis C virus. SSB protein was originally defined by its reactivity with autoantibodies from patients with Sjogren syndrome and systemic lupus erythematosus.La is involved in diverse aspects of RNA metabolism, including binding and protecting 3-prime UUU (OH) elements of newly RNA polymerase III (see MIM 606007)-transcribed RNA, processing 5-prime and 3-prime ends of pre-tRNA precursors, acting as an RNA chaperone, and binding viral RNAs associated with hepatitis C virus. La protein was originally defined by its reactivity with autoantibodies from patients with Sjogren syndrome (MIM 270150) and systemic lupus erythematosus La is involved in diverse aspects of RNA metabolism, including binding and protecting 3-prime UUU (OH) elements of newly RNA polymerase III (see MIM 606007)-transcribed RNA, processing 5-prime and 3-prime ends of pre-tRNA precursors, acting as an RNA chaperone, and binding viral RNAs associated with hepatitis C virus. La protein was originally defined by its reactivity with autoantibodies from patients with Sjogren syndrome (MIM 270150) and systemic lupus erythematosus (SLE; MIM 152700) (Teplova et al., 2006 [PubMed 16387655]).[supplied by OMIM]. Sequence Note: removed 1 base from the 3' end that did not align to the reference genome assembly. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Entrez Gene record to access additional publications. PRIMARYREFSEQ_SPAN PRIMARY_IDENTIFIER PRIMARY_SPAN COMP 1-1673 BC020818.1 1-1673

Supplier: Rockland Immunochemical

The innate immune system detects viral infection by recognizing various viral components and triggers antiviral responses. Like the toll-like receptor 3 (TLR3), the melanoma differentiation-associated protein 5 (MDA5) recognizes double-stranded (ds) RNA, a molecular pattern associated with viral infection. MDA5, a member of the DEAD/DEAH-box RNA helicase family, consists of an amino-terminal caspase recruitment domain (CARD) and a carboxyl-terminal RNA helicase domain similar to that of the related protein RIG-1. When stimulated by dsRNA, MDA5 recruits the adaptor protein VISA and ultimately causes the activation of IRF-3 and NF-kB. MDA5 and RIG-1 recognize different types of dsRNA, with MDA5 recognizing poly (I:C). MDA5-null mice were highly susceptible to infection with picornaviruses, which possess such sequences, demonstrating the importance of MDA5 in innate immunity.

Supplier: Rockland Immunochemical

Peripherin Antibody detects Peripherin. Peripherin is a ~57kDa intermediate filament subunit found initially in sensory neurons of the peripheral nervous systems, which gives the protein its name. Subsequently, peripherin was found in some sensory and other neurons of the central nervous system and also in PC12 cells. Peripherin is also expressed in certain neuroendocrine tumors and in the insulin producing cells of the pancreas. Peripherin belongs to the Class III family of intermediate filament subunits which also includes vimentin, glial fibrillary acidic protein (GFAP) and desmin. In contrast to the neurofilaments, peripherin is strongly up-regulated after nerve injury. Antibodies to peripherin can be used in identifying, classifying, and studying neurons throughout the nervous system. Peripherin is also a good diagnostic marker for ballooned axons seen in Lou Gehrig's disease (Amyotrophic lateral sclerosis) and some neuronally derived tumors. Autoantibodies to peripherin are frequently seen in the sera of patients with diabetes. Peripherin is not related to peripherin/RDS, a protein of the photoreceptor outer membrane mutations of which are causative of certain forms of slow retinal degeneration. Anti-Peripherin Antibody is ideal for investigators involved in Neuroscience and Cancer research.

Supplier: Prosci

GABRE belongs to the ligand-gated ionic channel (TC 1.A.9) family. It encodes the gamma-aminobutyric acid (GABA) A receptor which is a multisubunit chloride channel that mediates the fastest inhibitory synaptic transmission in the central nervous system. This gene encodes an epsilon subunit. It is mapped to chromosome Xq28 in a cluster comprised of genes encoding alpha 3, beta 4 and theta subunits of the same receptor. Alternatively spliced transcript variants encoding different isoforms have been identified.

Supplier: Prosci

The ATP7A gene encodes the Menkes copper-translocating P-type ATPase, a ubiquitous protein that regulates the absorption of copper in the gastrointestinal tract. Inside cells, this protein has a dual function: it delivers copper to cuproenzymes in the Golgi compartment and effluxes excess copper. The trafficking mechanism and catalytic activity combine to facilitate absorption and intercellular transport of copper. Menkes disease, a systemic copper deficiency disorder, is caused by mutations in the ATP7A gene.

Supplier: Prosci

CES1 is one of the enzymes responsible for the hydrolysis of ester- and amide-bond-containing drugs such as cocaine and heroin. They also hydrolize long-chain fatty acid esters and thioesters. This enzyme is known to hydrolyze aromatic and aliphatic esters and is necessary for cellular cholesterol esterification. It may also play a role in detoxification in the lung and/or protection of the central nervous system from ester or amide compounds. Carboxylesterase deficiency may be associated with non-Hodgkin lymphoma or B-cell lymphocytic leukemia.Carboxylesterase 1 is a member of a large multigene family. The enzymes encoded by these genes are responsible for the hydrolysis of ester- and amide-bond-containing drugs such as cocaine and heroin. They also hydrolize long-chain fatty acid esters and thioesters. This enzyme is known to hydrolyze aromatic and aliphatic esters and is necessary for cellular cholesterol esterification. It may also play a role in detoxification in the lung and/or protection of the central nervous system from ester or amide compounds. Carboxylesterase deficiency may be associated with non-Hodgkin lymphoma or B-cell lymphocytic leukemia. Three transcript variants encoding three different isoforms have been found for this gene.

Supplier: Cube Biotech

HighSpec Rho1D4 MagBeads XL is a suspension of 90 µm magnetic agarose beads coupled to an anti-Rho1D4 antibody.

Supplier: Enzo Life Sciences

The 70 kDa heat shock protein Hsp70 belongs to the Hsp70 family of highly-related protein isoforms ranging in size from 66 kDa to 78 kDa. Hsc70 shares close biochemical and biological ties to Hsp70, and also belongs to the Hsp70 family. These proteins include cognate members found within major intracellular compartments and highly inducible isoforms predominantly cytoplasmic or nuclear in distribution. Members of the Hsp70 family function as molecular chaperones involved in such cellular functions as protein folding, transport, maturation and degradation, operating in an ATP-dependent manner. The molecular chaperones of the Hsp70 family recognize and bind to nascent polypeptide chains or partially folded intermediates of proteins, preventing their aggregation and misfolding, and the binding of ATP triggers a critical conformational change leading to the release of the bound substrate protein. Data demonstrates that with a ubiquitin-like domain at its amino terminus and its association with the 26S proteosome in HeLa cells, Bag-1 modulates the chaperone activity of Hsc70 and Hsp70. These findings reveal Bag-1's role as a physical link between the Hsc70/Hsp70 chaperone system and the proteasome. Experimental data also shows that the ATPase domain and the substrate binding domain of Hsp70 (or Hsc70) cooperate to form a co-chaperone-chaperone complex with the synaptic vesicle cysteine string protein (csp), essential for normal neurotransmitter release.

Supplier: Prosci

B2M Antibody: Beta2-microglobulin (B2M) is a principal component of the Major Histocompatibility Complex (MHC) class I molecule, a ternary membrane protein complex that displays fragments derived from proteolyzed cytosolic proteins on the surface of cells for recognition by the surveillance immune system (1,2). B2M is involved in the presentation of peptide antigens to the immune system and plays a critically important role in immune system function. It is expressed on nearly all nucleated cells and contains one Ig-like C1-type (immunoglobulin-like) domain. Mutations in the Beta 2-microglobulin gene can enhance the progression of malignant melanoma and osteoarthropathy (4,5).

Supplier: Bioss

The innate immune system detects viral infection by recognizing various viral components and triggers antiviral responses. Like the toll-like receptor 3 (TLR3), the cytoplasmic helicase retinoic acid inducible gene protein 1 (RIG1/DDX58) recognizes double-stranded (ds) RNA, a molecular pattern associated with viral infection. Unlike TLR3 however, RIG1/DDX58 activates the kinases TBK1 and IKKe through the adaptor protein IPS1. These kinases then phosphorylate the transcription factors IRF3 and IRF7 which are essential for the expression of type-I interferons. RIG1/DDX58 is required for the production of interferons in response to RNA viruses including paramyxoviruses, influenza virus, and Japanese encephalitis virus.

Supplier: Prosci

Apurinic/apyrimidinic (AP) sites occur frequently in DNA molecules by spontaneous hydrolysis, by DNA damaging agents or by DNA glycosylases that remove specific abnormal bases. AP sites are pre-mutagenic lesions that can prevent normal DNA replication so the cell contains systems to identify and repair such sites. Class II AP endonucleases cleave the phosphodiester backbone 5' to the AP site. This gene encodes the major AP endonuclease in human cells.

Supplier: Bioss

Growth/differentiation factors (GDFs) are members of the TGF superfamily (1,2). Members of the TGF superfamily are involved in embryonic development and adult tissue homeostasis (1). GDF-1 expression is almost exclusively restricted to the central nervous system and mediates cell differentiation events during embryonic development (3). Neither GDF-3 (Vgr-2) nor GDF-9 contains the conserved cysteine residue which is found in most other TGF superfamily members. GDF-3 is detectable in bone marrow, spleen, thymus and adipose tissue, whereas GDF-9 has only been detected in ovary (4). GDF-5 (also designated CDMP-1) has been shown to induce activation of plasminogen activator, thereby inducing angiogenesis. It is predominantly expressed in long bones during fetal embryonic development and is involved in bone formation. (5). GDF-5 mutations have been identified in mice with the mutation brachypodism (bp), a mutation which affects the length and number of bones in limbs (6). GDF-6 and GDF-7 are closely related to GDF-5 (6). GDF-8 has been shown to be a negative regulator of skeletal muscle mass (1).

Supplier: FUJIFILM IRVINE SCIENTIFIC WAKO CHE

This antibody is Anti PA tag, Monoclonal Antibody conjugated horse radish peroxidase.

Supplier: Biosensis

The amyloid beta peptide is derived from the cleavage of the Amyloid precursor protein (APP) and varies in length from 39 to 43 amino acids. However, the form(s) of amyloid-beta peptide (Aβ) associated with the pathology characteristic of Alzheimer’s disease (AD) remains unclear. In particular, the neurotoxicity of intraneuronal Aβ accumulation is an area of considerable research and controversy principally because antibodies thought to be specific for Aβ have been shown to actually detect intraneuronal APP and not Aβ exclusively. MOAB-2 (mouse IgG2b) is a pan-specific, high-titer antibody to Aβ residues 1-4 as demonstrated by biochemical and immunohistochemical analyses (IHC), and is highly specific just to amyloid beta peptide. MOAB-2 did not detect APP or APP-CTFs in cell culture media/lysates (HEK-APPSwe or HEK APPSwe/BACE1) or in brain homogenates from transgenic mice expressing 5 familial AD (FAD) mutation (5xFAD mice). Using IHC on 5xFAD brain tissue, MOAB-2 immunoreactivity co-localized with C-terminal antibodies specific for Aβ40 and Aβ42. MOAB-2 did not co-localize with either N- or C-terminal antibodies to APP. In addition, no MOAB-2-immunreactivity was observed in the brains of 5xFAD/BACE-/- mice, although significant amounts of APP were detected by N- and C-terminal antibodies to APP, as well as by 6E10. In both 5xFAD and 3xTg mouse brain tissue, MOAB-2 co-localized with cathepsin-D, a marker for acidic organelles, further evidence for intraneuronal Aβ, distinct from Aβ associated with the cell membrane. MOAB-2 demonstrated strong intraneuronal and extra-cellular immunoreactivity in 5xFAD and 3xTg mouse brain tissues.

Supplier: Biotium

Fluorescent cholera toxin subunit B (CTB) conjugates that are optimized for direct stochastic optical reconstruction microscopy (dSTORM) imaging of EVs and exosomes.

Supplier: Proteintech

FXYD2 (FXYD domain-containing ion transport regulator 2), also known as the gamma-subunit of the NaK-ATPase, belongs to the FXYD family which has been proposed to be the regulators of Na, K-ATPase function by lowering affinities of the system for potassium and sodium. The expression of FXYD2 is most abundant in kidney, while it is also detected in several other tissues like placenta, pancreas, and dorsal root ganglia (DRGs). Three splice variants of FXYD2 have been reported in mouse kidney, namely FXYD2 γa, -γb,and -γc. FXYD2 γa has been identified as a pancreatic beta cell-specific biomarker. This antibody can recognize all three isoforms of FXYD2.

Supplier: Prosci

Homeobox-containing genes are thought to have a role in controlling development. In Drosophila, the 'engrailed' (en) gene plays an important role during development in segmentation, where it is required for the formation of posterior compartments. Different mutations in the mouse homologs, En1 and En2, produced different developmental defects that frequently are lethal. The human engrailed homologs 1 and 2 encode homeodomain-containing proteins and have been implicated in the control of pattern formation during development of the central nervous system.Homeobox-containing genes are thought to have a role in controlling development. In Drosophila, the 'engrailed' (en) gene plays an important role during development in segmentation, where it is required for the formation of posterior compartments. Different mutations in the mouse homologs, En1 and En2, produced different developmental defects that frequently are lethal. The human engrailed homologs 1 and 2 encode homeodomain-containing proteins and have been implicated in the control of pattern formation during development of the central nervous system. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Entrez Gene record to access additional publications.

Supplier: Prosci

CYBB is a critical component of the membrane-bound oxidase of phagocytes that generates superoxide. It is the terminal component of a respiratory chain that transfers single electrons from cytoplasmic NADPH across the plasma membrane to molecular oxygen on the exterior. It also functions as a voltage-gated proton channel that mediates the H (+) currents of resting phagocytes. It participates in the regulation of cellular pH and is blocked by zinc. Defects in CYBB are a cause of X-linked chronic granulomatous disease (X-CGD).Cytochrome b (-245) is composed of cytochrome b alpha (CYBA) and beta (CYBB) chain. It has been proposed as a primary component of the microbicidal oxidase system of phagocytes. CYBB deficiency is one of five described biochemical defects associated with chronic granulomatous disease (CGD). In this disorder, there is decreased activity of phagocyte NADPH oxidase; neutrophils are able to phagocytize bacteria but cannot kill them in the phagocytic vacuoles. The cause of the killing defect is an inability to increase the cell's respiration and consequent failure to deliver activated oxygen into the phagocytic vacuole. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Entrez Gene record to access additional publications.

Supplier: Prosci

TPM1 is a member of the tropomyosin family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells. Tropomyosin is composed of two alpha-helical chains arranged as a coiled-coil. It is polymerized end to end along the two grooves of actin filaments and provides stability to the filaments. The protein is one type of alpha helical chain that forms the predominant tropomyosin of striated muscle, where it also functions in association with the troponin complex to regulate the calcium-dependent interaction of actin and myosin during muscle contraction.This gene is a member of the tropomyosin family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells. Tropomyosin is composed of two alpha-helical chains arranged as a coiled-coil. It is polymerized end to end along the two grooves of actin filaments and provides stability to the filaments. The encoded protein is one type of alpha helical chain that forms the predominant tropomyosin of striated muscle, where it also functions in association with the troponin complex to regulate the calcium-dependent interaction of actin and myosin during muscle contraction. In smooth muscle and non-muscle cells, alternatively spliced transcript variants encoding a range of isoforms have been described. Mutations in this gene are associated with type 3 familial hypertrophic cardiomyopathy.

Supplier: Bioss

The oncogene BCL2 is a membrane protein that blocks a step in a pathway leading to apoptosis or programmed cell death. The protein encoded by this May play a role in the immune system processes. Protects cells from FAS-, TNF alpha- and FADD-induced apoptosis without increasing expression of the inhibitors of apoptosis BCL2 and BCLXL. Seems to activate an inhibitory pathway that prevents CASP8 activation following FAS stimulation, rather than blocking apoptotic signals downstream. May inhibit FAS-induced apoptosis by preventing CASP8 processing through CFLAR up-regulation.Tissue specificity: Expressed in lymph nodes, peripheral blood leukocytes, lung, thymus and kidneys. Very weak expression detected in spleen, liver, heart, and salivary gland.

Supplier: Bioss

Growth/differentiation factors (GDFs) are members of the TGF superfamily (1,2). Members of the TGF superfamily are involved in embryonic development and adult tissue homeostasis (1). GDF-1 expression is almost exclusively restricted to the central nervous system and mediates cell differentiation events during embryonic development (3). Neither GDF-3 (Vgr-2) nor GDF-9 contains the conserved cysteine residue which is found in most other TGF superfamily members. GDF-3 is detectable in bone marrow, spleen, thymus and adipose tissue, whereas GDF-9 has only been detected in ovary (4). GDF-5 (also designated CDMP-1) has been shown to induce activation of plasminogen activator, thereby inducing angiogenesis. It is predominantly expressed in long bones during fetal embryonic development and is involved in bone formation. (5). GDF-5 mutations have been identified in mice with the mutation brachypodism (bp), a mutation which affects the length and number of bones in limbs (6). GDF-6 and GDF-7 are closely related to GDF-5 (6). GDF-8 has been shown to be a negative regulator of skeletal muscle mass (1).

Supplier: Prosci

FUNCTION: Electrically silent transporter system. Mediates sodium and chloride reabsorption. Plays a vital role in the regulation of ionic balance and cell volume.
SIMILARITY: Belongs to the SLC12A transporter family.
SUBCELLULAR LOCATION: Membrane; multi-pass membrane protein.
TISSUE SPECIFICITY: Expressed in many tissues.

Supplier: Prosci

Angiotensin II is a potent vasopressor hormone and a primary regulator of aldosterone secretion. It is an important effector controlling blood pressure and volume in the cardiovascular system. It acts through at least two types of receptors. AGTR1 is the type 1 receptor which is thought to mediate the major cardiovascular effects of angiotensin II. AGTR1 may play a role in the generation of reperfusion arrhythmias following restoration of blood flow to ischemic or infarcted myocardium. It was previously thought that a related gene, denoted as AGTR1B, existed; however, it is now believed that there is only one type 1 receptor gene in humans.Angiotensin II is a potent vasopressor hormone and a primary regulator of aldosterone secretion. It is an important effector controlling blood pressure and volume in the cardiovascular system. It acts through at least two types of receptors. This gene encodes the type 1 receptor which is thought to mediate the major cardiovascular effects of angiotensin II. This gene may play a role in the generation of reperfusion arrhythmias following restoration of blood flow to ischemic or infarcted myocardium. It was previously thought that a related gene, denoted as AGTR1B, existed; however, it is now believed that there is only one type 1 receptor gene in humans. At least five transcript variants have been described for this gene. Additional variants have been described but their full-length nature has not been determined. The entire coding sequence is contained in the terminal exon and is present in all transcript variants.

Supplier: Prosci

PADI2 encodes a member of the peptidyl arginine deiminase family of enzymes, which catalyze the post-translational deimination of proteins by converting arginine residues into citrullines in the presence of calcium ions. The family members have distinct substrate specificities and tissue-specific expression patterns. The type II enzyme is the most widely expressed family member. Known substrates for this enzyme include myelin basic protein in the central nervous system and vimentin in skeletal muscle and macrophages. PADI2 is thought to play a role in the onset and progression of neurodegenerative human disorders, including Alzheimer disease and multiple sclerosis, and it has also been implicated in glaucoma pathogenesis.This gene encodes a member of the peptidyl arginine deiminase family of enzymes, which catalyze the post-translational deimination of proteins by converting arginine residues into citrullines in the presence of calcium ions. The family members have distinct substrate specificities and tissue-specific expression patterns. The type II enzyme is the most widely expressed family member. Known substrates for this enzyme include myelin basic protein in the central nervous system and vimentin in skeletal muscle and macrophages. This enzyme is thought to play a role in the onset and progression of neurodegenerative human disorders, including Alzheimer disease and multiple sclerosis, and it has also been implicated in glaucoma pathogenesis. This gene exists in a cluster with four other paralogous genes. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Entrez Gene record to access additional publications.

Supplier: Rockland Immunochemical

IL-16 was initially identified as a chemotactic cytokine, but is now known to possess a wide range of activities. Later studies have more fully characterized IL-16 as an immunomodulatory cytokine that contributes to the regulatory process of CD4+ T cell recruitment and activation at sites of inflammation in association with asthma and several autoimmune diseases. The precursor of IL-16 (pro-IL-16) is thought to be cleaved towards the C-terminal region by Caspase-3, releasing a 20 kDa active form that binds to and signals through CD4. Besides acting as a chemotactic cytokine, IL-16 is thought to also be involved in the regulation of T cell proliferation and multiple infectious, immune-mediated, and autoimmune inflammatory disorders including irritable bowel syndrome, systemic lupus erythematosus, and neurodegenerative disorders. At least two isoforms of IL-16 are known to exist; the longer isoform (also known as NIL-16) is detected only in neurons of the cerebellum and hippocampus.

Supplier: Enzo Life Sciences

Kit for generation of SUMOylated proteins in vitro.

Supplier: Bioss

The innate immune system detects viral infection by recognizing various viral components and triggers antiviral responses. Like the toll-like receptor 3 (TLR3), the cytoplasmic helicase retinoic acid inducible gene protein 1 (RIG1/DDX58) recognizes double-stranded (ds) RNA, a molecular pattern associated with viral infection. Unlike TLR3 however, RIG1/DDX58 activates the kinases TBK1 and IKKe through the adaptor protein IPS1. These kinases then phosphorylate the transcription factors IRF3 and IRF7 which are essential for the expression of type-I interferons. RIG1/DDX58 is required for the production of interferons in response to RNA viruses including paramyxoviruses, influenza virus, and Japanese encephalitis virus.

Supplier: Prosci

CCR4 belongs to the G-protein-coupled receptor family. It is a receptor for the CC chemokine - MIP-1, RANTES, TARC and MCP-1. Chemokines are a group of small polypeptide, structurally related molecules that regulate cell trafficking of various types of leukocytes. The chemokines also play fundamental roles in the development, homeostasis, and function of the immune system, and they have effects on cells of the central nervous system as well as on endothelial cells involved in angiogenesis or angiostasis. The protein encoded by this gene belongs to the G-protein-coupled receptor family. It is a receptor for the CC chemokine - MIP-1, RANTES, TARC and MCP-1. Chemokines are a group of small polypeptide, structurally related molecules that regulate cell trafficking of various types of leukocytes. The chemokines also play fundamental roles in the development, homeostasis, and function of the immune system, and they have effects on cells of the central nervous system as well as on endothelial cells involved in angiogenesis or angiostasis. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Entrez Gene record to access additional publications. PRIMARYREFSEQ_SPAN PRIMARY_IDENTIFIER PRIMARY_SPAN COMP 1-1657 BC071751.1 1-1657

Supplier: Prosci

VSX1 contains a paired-like homeodomain and binds to the core of the locus control region of the red/green visual pigment gene cluster. VSX1 may regulate expression of the cone opsin genes early in development. Mutations in VSX1 can cause posterior polymorphous corneal dystrophy and keratoconus. Alternatively spliced transcript variants encoding different isoforms have been described.The protein encoded by this gene contains a paired-like homeodomain and binds to the core of the locus control region of the red/green visual pigment gene cluster. The encoded protein may regulate expression of the cone opsin genes early in development. Mutations in this gene can cause posterior polymorphous corneal dystrophy and keratoconus. Alternatively spliced transcript variants encoding different isoforms have been described.