|
Amoebocyte
An amebocyte or amoebocyte () is a mobile cell (moving like an amoeba) in the body of invertebrates including cnidaria, echinoderms, molluscs, tunicates, sponges and some chelicerates. They move by pseudopodia. Similarly to some of the white blood cells of vertebrates, in many species amebocytes are found in the blood or body fluid and play a role in the defense of the organism against pathogens. Depending on the species, an amebocyte may also digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types. Limulus amebocyte lysate, an aqueous extract of amebocytes from the Atlantic horseshoe crab (''Limulus polyphemus''), is commonly used in a test to detect bacterial endotoxins. In sponges, amebocytes, also known as archaeocytes, are cells found in the mesohyl that can transform into any of the animal's more specialized cell types. In tunicates they are blood cells and use pseudopodia to attack pathogens that enter the bloo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeocyte
Archaeocytes (from Greek '' archaios'' "beginning" and '' kytos'' "hollow vessel") or amoebocytes are amoeboid cells found in sponges. They are totipotent and have varied functions depending on the species. The structure of these cells match to that of the stem cells as of containing high cytoplasmic content that helps the cells to morph according to their function. Location Archaeocytes are along with other specialized sponge cells including collencytes and structural elements called spicules. They move about within the mesohyl with amoeba-like movements performing a number of important functions. Functions Cellular differentiation is an essential function of the archaeocyte. All specialized cells within the sponge have its origins with the archaeocyte. This is especially important in reproduction as the sex cells of the sponge in sexual reproduction are formed from these amoeboid cells. Similarly in asexual reproduction amoebocytes result in the formation of gemmules which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Cell
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites.Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecular Biology of the Cell '' fourth edition, edited by Bruce Alberts (2002) published by Garland Science. The Alberts text discusses how the "cellular building blocks" move to shape developing s. It is also common to des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ''pathogen'' came into use in the 1880s. Typically, the term ''pathogen'' is used to describe an ''infectious'' microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them. There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the longest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunica (biology)
In biology, a tunica (, ; ) is a layer, coat, sheath, or similar covering. The word came to English from the New Latin of science and medicine. Its literal sense is about the same as that of the word ''tunic'', with which it is cognate. In biology one of its senses used to be the taxonomic name of a genus of plants, but the nomenclature has been revised and those plants are now included in the genus ''Petrorhagia''. In modern biology in general, ''tunica'' occurs as a technical or anatomical term mainly in botany and zoology. It usually refers to membranous structures that line or cover particular organs. In many such contexts ''tunica'' is used interchangeably with ''tunic'' according to preference. An organ or organism that has a tunic(a) may be said to be ''tunicate'', as in a ''tunicate bulb''. This adjective ''tunicate'' is not to be confused with the noun ''tunicate'', which refers to a member of the subphylum '' Tunicata''. Botanical and related usages In botany there are s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudopodia
A pseudopod or pseudopodium (plural: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and may also contain microtubules and intermediate filaments. Pseudopods are used for motility and ingestion. They are often found in amoebas. Different types of pseudopodia can be classified by their distinct appearances. Lamellipodia are broad and thin. Filopodia are slender, thread-like, and are supported largely by microfilaments. Lobopodia are bulbous and amoebic. Reticulopodia are complex structures bearing individual pseudopodia which form irregular nets. Axopodia are the phagocytosis type with long, thin pseudopods supported by complex microtubule arrays enveloped with cytoplasm; they respond rapidly to physical contact. Some pseudopodial cells are able to use multiple types of pseudopodia depending on the situation: Most of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Differentiation
Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Although metabolic composition does get altered quite dramaticall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesohyl
The mesohyl, formerly known as mesenchyme or as mesoglea, is the gelatinous matrix within a sponge. It fills the space between the external pinacoderm and the internal choanoderm. The mesohyl resembles a type of connective tissue and contains several amoeboid cells such as amebocytes, as well as fibrils and skeletal elements. For a long time, it has been largely accepted that sponges lack true tissue, but it is currently debated as to whether mesohyl and pinacoderm layers are tissues. The mesohyl is composed of the following main elements: collagen, fibronectin-like molecules, galectin, and a minor component, dermatopontin. These polypeptides form the extracellular matrix which provides the platform for specific cell adhesion as well as for signal transduction and cellular growth. The mesohyl includes a noncellular colloidal mesoglea with embedded collagen fibers, spicules and various cells, being as such a type of mesenchyme Mesenchyme () is a type of loosely organiz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endotoxin
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer membrane of Gram-negative bacteria. Today, the term ''endotoxin'' is often used synonymously with LPS, although there are a few endotoxins (in the original sense of toxins that are inside the bacterial cell that are released when the cell disintegrates) that are not related to LPS, such as the so-called delta endotoxin proteins produced by '' Bacillus thuringiensis''. Lipopolysaccharides can have substantial impacts on human health, primarily through interactions with the immune system. LPS is a potent activator of the immune system and pyrogen (agent that causes fever). In severe cases, LPS can play a role in causing septic shock. In lower levels and over a longer time period, there is evidence LPS may play an important and harmful role ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationsh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantic Horseshoe Crab
The Atlantic horseshoe crab (''Limulus polyphemus''), also known as the American horseshoe crab, is a species of marine and brackish chelicerate arthropod. Despite their name, horseshoe crabs are more closely related to spiders, ticks, and scorpions than to crabs. It is found in the Gulf of Mexico and along the Atlantic coast of North America. The main area of annual migration is Delaware Bay along the South Jersey Delaware Bayshore. Their eggs were eaten by Native Americans, but today Atlantic horseshoe crabs are caught for use as fishing bait, in biomedicine (especially for ''Limulus'' amebocyte lysate) and science. They play a major role in the local ecosystems, with their eggs providing an important food source for shorebirds, and the juveniles and adults being eaten by sea turtles. The other three extant (living) species in the family Limulidae are also called horseshoe crabs, but they are restricted to Asia. Names and classification This group of animals is also known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limulus Amebocyte Lysate
Limulus amebocyte lysate (LAL) is an aqueous extract of blood cells (amoebocytes) from the Atlantic horseshoe crab ''Limulus polyphemus''. LAL reacts with bacterial endotoxin lipopolysaccharide (LPS), which is a membrane component of gram-negative bacteria. This reaction is the basis of the LAL test, which is widely used for the detection and quantification of bacterial endotoxins. In Asia, a similar Tachypleus amebocyte lysate (TAL) test based on the local horseshoe crabs ''Tachypleus gigas'' or ''Tachypleus tridentatus'' is occasionally used instead. The recombinant factor C (rFC) assay is a replacement of LAL/TAL based on a similar reaction. Background The American medical researcher Fred Bang reported in 1956 that gram-negative bacteria, even if killed, will cause the blood of the horseshoe crab to turn into a semi-solid mass. It was later recognized that the animal's blood cells, mobile cells called amoebocytes, contain granules with a clotting factor known as coaguloge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following: * jawless fish, which include hagfish and lampreys * jawed vertebrates, which include: ** cartilaginous fish (sharks, rays, and ratfish) ** bony vertebrates, which include: *** ray-fins (the majority of living bony fish) *** lobe-fins, which include: **** coelacanths and lungfish **** tetrapods (limbed vertebrates) Extant vertebrates range in size from the frog species ''Paedophryne amauensis'', at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.svg "Click for more on -> Cellular Differentiation")
.jpg "Click for more on -> Limulus Amebocyte Lysate")
