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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A class of prokaryotic organisms coextensive with the division Prochlorophycota in the kingdom Monera. Because prochlorophytes carry out oxygen-evolving photosynthesis, they may be considered algae. They are distinguished from Cyanophyceae, the only other prokaryotic algae, by the presence in their photosynthetic lamellae of chlorophyll <i>b</i> in addition to chlorophyll <i>a</i> and the absence of phycobilin pigments. Otherwise, they resemble Cyanophyceae biochemically and ultrastructurally. The class comprises a single genus, <i>Prochloron</i>, with one species.
Industry:Science
A class of proteins of nonimmune origin that bind carbohydrates reversibly and noncovalently without inducing any change in the carbohydrate. Since their discovery in 1888, lectins have been labeled agglutinins, antibodylike molecules, hemagglutinins, heteroagglutinins, heterophile agglutinins, natural or normal antibodies, protectins, phytohemagglutinins, and receptor-specific proteins, among other names. The main feature of lectins is their ability to recognize and bind specific carbohydrate structures becoming the translators of the sugar code (the coding of biological information by sugar structures). Lectins bind a variety of cells having cell-surface glycoproteins (carbohydrate-bound proteins) or glycolipids (carbohydrate-bound lipids). The presence of two or more binding sites for each lectin molecule allows the agglutination (clumping) of many cell types, and the agglutination reaction has been used extensively to detect the presence of lectins in extracts from different organisms. However, multivalency (having several sites of attachment) may not be an absolute requirement, even though it is still an important factor for most lectins. Lectins are ubiquitous in nature and may have very different roles according to the organism, tissue, or developmental stage. Their potential ligands, simple or complex carbohydrates, are present in all living cells and in biological fluids, which suggests that protein–carbohydrate interactions constitute basic phenomena common to all organisms.
Industry:Science
A class of protozoa of the subphylum Sarcomastigophora. Zoomastigophorea, also known as Zoomastigina, are flagellates which have few or no characters relating them to the pigmented forms. Some are simple, some are specialized; some have pseudopodia besides flagella, others have no pseudopodia. One group engulfs solid food at any body point; another shows localized ingestive areas. All are colorless. None produce starch or paramylum, and lipids and glycogen are assimilation products. Cells are naked or have delicate membranes. Colony formation is common. Colonies differ greatly in form and may be amorphous, linear, spherical, arboroid, or plane. Flagella vary from none to many. Nuclei generally have endosomes; frequently a rhizostyle extends from the nucleus to the flagellum base. Nutrition is holozoic, saprozoic, or parasitic, and encystment is common. Ecologically Zoomastigophorea are adapted to waters of relatively high organic content, but they occur in the clearest fresh waters and in the high seas. Nine orders are included in this class: the Choanoflagellida, Bicosoecida, Rhizomastigida, Kinetoplastida, Retortomonadida, Diplomonadida, Oxymonadida, Trichomonadida, and Hypermastigida. See articles on these orders.
Industry:Science
A class of protozoa, often known as Acnidosporidia, in the subphylum Sporozoa. Haplosporea are distinguished from other similar groups by the production of spores lacking polar filaments. The spores are enclosed in a membrane, and each spore contains a single sporozoite.
Industry:Science
A class of Sarcodina including both parasitic and free-living species found in fresh and salt water and the soil. No species forms true axopodia; instead, pseudopodia may be filopodia, lobopodia, or reticulopodia; or there may be no pseudopodia in some cases. Rhizopodea include five subclasses: Lobosia, Fiosia, Granuloreticulosia, Mycetozoia, and Labyrinthulia. Lobosia are amebas and testate rhizopods with lobopodia. Filosia are naked or testate species with filopodia. Granuloreticulosia are noted for their reticulopodia, which often fuse into extensive networks. A bidirectional flow of cytoplasm typically moves granules into opposite directions along the two sides of a single pseudopodium. Mycetozoia are a heterogeneous collection, including both cellular and true slime molds. Labyrinthulia are unique protozoa which form no obvious pseudopodia, but move by still undetermined methods on or inside secreted tubules. Many Rhizopodea are phagotrophic, but ingestion has not been described in Labyrinthulia. A test may be present or absent in different genera of Lobosia, Filosia, and Granuloreticulosia.
Industry:Science
A class of Sarcodina; or in some modern schemes a superclass (Actinopoda) within the phylum Sarcomastigophora. Some of these protozoans have more or less permanent pseudopodia, composed of a central shaft of microtubules surrounded by a thin cytoplasmic envelope (axopodia); others have delicate and often radially arranged filopodia (filamentous, flexible pseudopodia) or filoreticulopodia (filamentous, branched pseudopodia) without axial microtubules. Although some are stalked and attached to the substratum (sessile), most are floating types. There are four subclasses: Radiolaria (Polycystinea and Phaeodarea), Acantharia, Heliozoia, and Proteomyxidia.
Industry:Science
A class of simple sugars containing a chain of 3–10 carbon atoms in the molecule, known as polyhydroxy aldehydes (aldoses) or ketones (ketoses). They are very soluble in water, sparingly soluble in ethanol, and insoluble in ether. The number of monosaccharides known is approximately 70, of which about 20 occur in nature. The remainder are synthetic. The existence of such a large number of compounds is due to the presence of asymmetric carbon atoms in the molecules. Aldohexoses, for example, which include the important sugar glucose, contain no less than four asymmetric atoms, each of which may be present in either <small>D</small> or <small>L</small> configuration. The number of stereoisomers rapidly increases with each additional asymmetric carbon atom.
Industry:Science
A class of sponges that lay down a compound skeleton comprising an external, basal mass of calcium carbonate, either aragonite or calcite, and internal siliceous spicules and protein fibers. The living tissue forms a thin layer over the basal calcareous skeleton and extends into its surface depressions; the organization of the tissue is similar to that of encrusting demosponges. Sclerosponges are common inhabitants of cryptic habitats on coral reefs in both the Caribbean and Indo-Pacific biogeographic regions. Their discovery has reopened questions of the affinities of certain fossil reef–inhabiting organisms, the stromatoporoids and the chaetetid and favositid tabulate “corals,” all of which have been generally regarded as members of the phylum Cnidaria.
Industry:Science
A class of sponges whose skeletons are made of siliceous hexactine spicules. These exclusively marine sponges are widely distributed in modern oceans. Their fossil record extends from the late Precambrian to the Recent. The basic spicule type of the class is a triaxial hexactine, in which the three pairs of opposed rays are at right angles to each other and lie along one of the three axes of a cube. Proximal ray ends and axial filaments meet at the center of the cube. These principal spicules and variants of that form make up skeletons of the sponges.
Industry:Science
A class of teleostom fishes commonly known as the ray-finned fishes comprising the subclasses Cladistia (Polypteriformes and fossil orders), Chondrostei (Acipenseriformes and fossil orders), and Neopterygii (the remaining actinopterygian orders). The Neopterygii, minus the Lepisosteiformes, Amiiformes, and several fossil taxa, comprise the Teleostei (see <b>illustration</b>). The Actinopterygii comprise about half of all vertebrate species and about 96% of all currently existing fishes. It is considered a nonmonophyletic group that is derived from more than one lineage when tetrapods are excluded. The Actinopterygii and the Sarcopterygii, minus the Tetrapoda, comprise what was previously called Osteichthyes (the bony fishes). The class includes 44 orders, 453 families, 4289 genera, and about 27,000 described extant species. Many species are known to science but are not yet described; further, in regions such as the Amazon and Congo basins, species are probably becoming extinct before they are discovered and described in the scientific literature.
Industry:Science
