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28-578: The antibody cocktail binds to cytokeratin 1 - 8, 10, 14 - 16 and 19 (but not CK17 or CK18). It is therefore used as a marker of carcinomas, such as depth of invasion and metastases. For example, it is both relatively sensitive and specific for detection of breast cancer metastasis to sentinel lymph nodes . It may cross-react with GFAP , leading to aberrant staining of glial tumors such as ependymoma , glioblastoma and schwannoma . It may also stain myofibroblasts and smooth muscle cells. Furthermore, it may stain nodal epithelial cells that has contaminated

56-416: A defense strategy. A solid glass cytoplasm would freeze subcellular structures in place, preventing damage, while allowing the transmission of tiny proteins and metabolites, helping to kickstart growth upon the cell's revival from dormancy . Research has examined the motion of cytoplasmic particles independent of the nature of the cytoplasm. In such an alternative approach, the aggregate random forces within

84-482: A tumor from recent biopsy. This article related to pathology is a stub . You can help Misplaced Pages by expanding it . Cytokeratin Cytokeratins are keratin proteins found in the intracytoplasmic cytoskeleton of epithelial tissue . They are an important component of intermediate filaments , which help cells resist mechanical stress. Expression of these cytokeratins within epithelial cells

112-509: A way of storing lipids such as fatty acids and sterols . Lipid droplets make up much of the volume of adipocytes , which are specialized lipid-storage cells, but they are also found in a range of other cell types. The cytoplasm, mitochondria, and most organelles are contributions to the cell from the maternal gamete. Contrary to the older information that disregards any notion of the cytoplasm being active, new research has shown it to be in control of movement and flow of nutrients in and out of

140-422: Is dependent on the manner in which signaling molecules are allowed to diffuse across the cell. While small signaling molecules like calcium ions are able to diffuse with ease, larger molecules and subcellular structures often require aid in moving through the cytoplasm. The irregular dynamics of such particles have given rise to various theories on the nature of the cytoplasm. There has long been evidence that

168-416: Is largely organ or tissue specific. The subsets of cytokeratins which an epithelial cell expresses depends mainly on the type of epithelium, the moment in the course of terminal differentiation and the stage of development. Thus a specific cytokeratin expression profile allows the identification of epithelial cells. Furthermore, this applies also to the malignant counterparts of the epithelia, ( carcinomas ), as

196-404: Is largely specific to particular organs or tissues. Thus they are used clinically to identify the cell of origin of various human tumors. The term cytokeratin began to be used in the late 1970s, when the protein subunits of keratin intermediate filaments inside cells were first being identified and characterized. In 2006 a new systematic nomenclature for mammalian keratins was created, and

224-399: The cytoplasm , keratin filaments associate laterally with each other to create bundles of ~50 nm radius. The radius of these bundles is set by the interplay between long range electrostatic repulsion and short range hydrophobic attraction. These keratin bundles span a complex network which extends from the surface of the nucleus to the cell membrane. Numerous accessory proteins are involved in

252-498: The cytosol (a gel-like substance), the organelles (the cell's internal sub-structures), and various cytoplasmic inclusions . The cytoplasm is about 80% water and is usually colorless. The submicroscopic ground cell substance, or cytoplasmic matrix, that remains after the exclusion of the cell organelles and particles is groundplasm . It is the hyaloplasm of light microscopy, a highly complex, polyphasic system in which all resolvable cytoplasmic elements are suspended, including

280-474: The protein filaments such as actin filaments and microtubules that make up the cytoskeleton, as well as soluble proteins and small structures such as ribosomes , proteasomes , and the mysterious vault complexes . The inner, granular and more fluid portion of the cytoplasm is referred to as endoplasm. Due to this network of fibres and high concentrations of dissolved macromolecules , such as proteins , an effect called macromolecular crowding occurs and

308-407: The vacuoles and sometimes the plastids. It remains uncertain how the various components of the cytoplasm interact to allow movement of organelles while maintaining the cell's structure. The flow of cytoplasmic components plays an important role in many cellular functions which are dependent on the permeability of the cytoplasm. An example of such function is cell signalling , a process which

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336-405: The ankyrin and spectrin complex protein network that underlies the cell membrane. Cytoplasm In cell biology , the cytoplasm describes all material within a eukaryotic cell , enclosed by the cell membrane , except for the cell nucleus . The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm . The main components of the cytoplasm are

364-452: The cell caused by motor proteins explain the non- Brownian motion of cytoplasmic constituents. The three major elements of the cytoplasm are the cytosol , organelles and inclusions . The cytosol is the portion of the cytoplasm not contained within membrane-bound organelles. Cytosol makes up about 70% of the cell volume and is a complex mixture of cytoskeleton filaments, dissolved molecules, and water. The cytosol's filaments include

392-404: The cytokeratin profile is generally retained. Thus the study of cytokeratin expression by immunohistochemistry techniques is a tool of immense value widely used for tumor diagnosis and characterization in surgical pathology . Does not react with hepatocytes and hepatocellular carcinoma The cytokeratins are encoded by a family encompassing 30 genes. Among them, 20 are epithelial genes and

420-426: The cytoplasm behaves like a sol-gel . It is thought that the component molecules and structures of the cytoplasm behave at times like a disordered colloidal solution (sol) and at other times like an integrated network, forming a solid mass (gel). This theory thus proposes that the cytoplasm exists in distinct fluid and solid phases depending on the level of interaction between cytoplasmic components, which may explain

448-490: The cytoplasm is a signaling activity for metabolic processes. In plants , movement of the cytoplasm around vacuoles is known as cytoplasmic streaming . The term was introduced by Rudolf von Kölliker in 1863, originally as a synonym for protoplasm , but later it has come to mean the cell substance and organelles outside the nucleus. There has been certain disagreement on the definition of cytoplasm, as some authors prefer to exclude from it some organelles, especially

476-579: The cytosol does not act as an ideal solution . This crowding effect alters how the components of the cytosol interact with each other. Organelles (literally "little organs") are usually membrane-bound structures inside the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria , the endoplasmic reticulum , the Golgi apparatus , vacuoles , lysosomes , and in plant cells, chloroplasts . The inclusions are small particles of insoluble substances suspended in

504-417: The cytosol. A huge range of inclusions exist in different cell types, and range from crystals of calcium oxalate or silicon dioxide in plants, to granules of energy-storage materials such as starch , glycogen , or polyhydroxybutyrate . A particularly widespread example are lipid droplets , which are spherical droplets composed of lipids and proteins that are used in both prokaryotes and eukaryotes as

532-434: The differential dynamics of different particles observed moving through the cytoplasm. A papers suggested that at length scale smaller than 100  nm , the cytoplasm acts like a liquid, while in a larger length scale, it acts like a gel. It has been proposed that the cytoplasm behaves like a glass -forming liquid approaching the glass transition . In this theory, the greater the concentration of cytoplasmic components,

560-421: The first and fourth residues are hydrophobic and the charged residues show alternate positive and negative polarity, resulting in the polar residues being located on one side of the helix. This central domain of the chain provides the molecular alignment in the keratin structure and makes the chains form coiled dimers in solution. The end-domain sequences of type I and II cytokeratin chains contain in both sides of

588-478: The function of the cytokeratin chain characteristic of a particular epithelial cell type. Two dimers of cytokeratin group into a keratin tetramer by anti-parallel binding. This cytokeratin tetramer is considered to be the main building block of the cytokeratin chain. By head-to-tail linking of the cytokeratin tetramers, the protofilaments are originated, which in turn intertwine in pairs to form protofibrils. Four protofibrils give place to one cytokeratin filament. In

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616-476: The genesis and maintenance of such structure. This association between the plasma membrane and the nuclear surface provides important implications for the organization of the cytoplasm and cellular communication mechanisms. Apart from the relatively static functions provided in terms of supporting the nucleus and providing tensile strength to the cell, the cytokeratin networks undergo rapid phosphate exchanges mediated depolymerization, with important implications in

644-454: The larger organelles such as the ribosomes , mitochondria , plant plastids , lipid droplets, and vacuoles . Many cellular activities take place within the cytoplasm, such as many metabolic pathways , including glycolysis , photosynthesis , and processes such as cell division . The concentrated inner area is called the endoplasm and the outer layer is called the cell cortex , or ectoplasm . Movement of calcium ions in and out of

672-404: The less the cytoplasm behaves like a liquid and the more it behaves as a solid glass, freezing more significant cytoplasmic components in place (it is thought that the cell's metabolic activity can fluidize the cytoplasm to allow the movement of such more significant cytoplasmic components). A cell's ability to vitrify in the absence of metabolic activity, as in dormant periods, may be beneficial as

700-431: The more dynamic cellular processes such as mitosis and post-mitotic period, cell movement and differentiation . Cytokeratins interact with desmosomes and hemidesmosomes, thus collaborating to cell–cell adhesion and basal cell–underlying connective tissue connection. The intermediate filaments of the eukaryotic cytoskeleton , which the cytokeratins are one of its three components, have been probed to associate also with

728-668: The proteins previously called cytokeratins are simply called keratins (human epithelial category). For example, cytokeratin-4 (CK-4) has been renamed keratin-4 (K4). However, they are still commonly referred to as cytokeratins in clinical practice. There are two categories of cytokeratins: the acidic type I cytokeratins and the basic or neutral type II cytokeratins . Within each category, cytokeratins are numbered in order of decreasing size, from high molecular weight (HMWCKs) to low molecular weight (LMWCKs). Cytokeratins are usually found in heterodimeric pairs of acidic and basic subunits of similar size. Expression of these cytokeratins

756-434: The remaining 10 are specific for trichocytes. All cytokeratin chains are composed of a central α-helix-rich domain (with a 50 to 90% sequence identity among cytokeratins of the same type and around 30% between cytokeratins of different type) with non-α-helical N- and C-terminal domains. The α-helical domain has 310-150 amino acids and comprises four segments in which a seven-residue pattern repeats. Into this repeated pattern,

784-447: The rod domain the subdomains V1 and V2, which have variable size and sequence. The type II also presents the conserved subdomains H1 and H2, encompassing 36 and 20 residues respectively. The subdomains V1 and V2 contain residues enriched by glycines and/or serines, the former providing the cytokeratin chain a strong insoluble character and facilitating the interaction with other molecules. These terminal domains are also important in defining

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