B
1-10 A B C D E F G H I J K L M N O P Q R S T U V W XYZB-Cell
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B-cells are B-lymphocytes, one of two major types of lymphocytes (the other being T-lymphocytes). B-lymphocytes' primary function is the production of antibodies.
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B-lymphocytes are white blood cells that develop in the bone marrow and then migrate to various parts of the body via the bloodstream. They are the basis for the body's humoral immune system since they produce and secrete immunoglobulins (antibodies) in response to antigens. B-lymphocytes represent about 5-15% of the circulating lymphoid pool and are classically defined by the presence of endogenously produced immunoglobulins.
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Bacillus is a large genus of gram-positive, spore-bearing, rod-like bacteria. They are widely distributed in soil and air (usually as spores). Most feed on dead organic material and are responsible for food spoilage.
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Background 15N is an isotope of nitrogen which is present in the human body in low concentrations (about 0.365%) at all times. The naturally present 15N is referred to as background 15N.
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Bacteria refers to a group of microorganisms which consist of only a single cell that lacks a distinct nuclear membrane and has a cell wall of unique composition. Bacteria are largely responsible for decay and decomposition of organic matter.
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Bactericidal is causing the death of bacteria.
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Bacteriology is the scientific study of bacteria.
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A bacteriophage is a virus that infects a bacterium or prokaryotes.
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Bacteriorhodopsin is a carotenoid (naturally occurring pigment found mostly in plants) analogous to rhodopsin, the pigment of the animal eye, which functions in vision. Bacteriorhodopsin is able to absorb light and generate a proton gradient across the membrane of halobacterium (a microbe), leading to ATP synthesis without the involvement of chlorophyll.
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Bacteriotherapy uses bacteria in the treatment of or control of disease; particularly intestinal diseases.
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Ballistic refers to the science of projectiles. Before the development of spacecraft capable of orbiting the Earth, ballistic missiles were launched. These missiles reached an environment of microgravity but followed a ballistic trajectory, still influenced by the Earth's gravity and atmospheric friction.
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Barophysiology is the study of the affects of air pressure on the body's physiology.
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A baroreceptor is a collection of sensory nerve endings specialized to monitor changes in blood pressure. The main receptors lie in the carotid sinuses and the aortic arch. Others are found in the walls of other large arteries and veins and some within the walls of the heart. Impulses from the receptors reach centers in the medulla, a part of the brain; from there autonomic activity is directed so that the heart rate and resistance of the peripheral blood vessels can be adjusted appropriately so that the necessary blood pressure is maintained.
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A baroreflex is a reflex instigated by a baroreceptor, a collection of sensory nerve endings specialized to monitor changes in blood pressure. The main receptors lie in the carotid sinuses and the aortic arch. Others are found in the walls of other large arteries and veins and some within the walls of the heart. Impulses from the receptors reach centers in the medulla; from here autonomic activity is directed so that the heart rate and resistance of the peripheral blood vessels can be adjusted appropriately. Thus, the baroreflex acts to increase or decrease the blood pressure through constant monitoring and reflex action in order to maintain the necessary blood pressure in the body.
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Barotitis media (or aerotitis media) is inflammation or bleeding in the middle ear caused by difference between the air pressure in the middle ear at of the atmosphere, as occurs in sudden changes in altitude. Symptoms are pain, tinnitus, diminished hearing, and vertigo.
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A "baseline" is a measurement which serves as a basis to which all following measurements are compared. An example: before exercise, your heart rate is measured. During exercise, your increased heart rate is measured and compared to your resting baseline measurement taken before exercise started.
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Basophils are granulocytes that can secrete biologically active substances such as histamine, proteoglycans and cyclooxigenase products. They are produced continually by stem cells in the bone marrow. The function of basophils is not fully understood, but it is known that they are capable of ingesting foreign particles and produce heparin and histamine (chemicals which induce inflammation), and are often associated with asthma and allergies. Related cells, mast cells, are often associated with helping provide mediators to initiate immune reponses.
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A batch technique is a technique utilized for the crystallization of proteins in which a solution that contains proteins along with other necessary chemical components is prepared and frozen prior to crystal formation.
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Bed rest studies are tests performed where the subject is confined to bed to simulate stays in space by reducing gravitational pull to the antigravity muscles and bones.
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Behavior and performance research conducted by NASA is designed to develop a knowledge of how space mission design and events, and spacecraft environment, affect the behavior and performance of crews. Countermeasures developed from this research will enhance the ability of humans in space and on the ground to cope with issues such as team problem-solving, decision-making and communication, team structure and expertise, cultural variability, uncertainty, stressors like isolation and confinement, and time pressure.
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Benzoic acid is an organic aromatic acid. It is commonly used as a preservative to inhibit the growth of bacteria and is sometimes as an antifungal agent.
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Globulins are a group of global proteins that are generally insoluble in water and present in blood, eggs, milk, and as a reserve protein in seeds. Blood serum globulins comprise four types: alpha-1, alpha-2, beta-globulins which serve as carrier proteins, and gamma-globulins which include the immunoglobulins responsible for immune responses.
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A beta ray is a stream of high speed electrons, or beta particles, emitted from a radioactive nucleus in beta decay.
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Beta-cloth is a glass fiber material characterized by extremely small diameter fibers, which provides a non-flammable, high temperature flame barrier.
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Beta-hemolytic refers to complete or true hemolysis, observed in blood agar cultures of various bacteria, especially hemolytic streptococci; virtually all of the erythrocytes are destroyed in a wide circular zone around the colony, thereby resulting in a clear "halo" of transparent agar; the zone of hemolysis is frequently much wider than the diameter of the colony.
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A bifurcation is a forking or division into two branches.
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A bigeminy is a condition in which alternate ectopic beats of the heart are transmitted to the pulse and felt as a double pulse beat.
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Bilateral means appearing or occurring on two sides.
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Bilirubin is one bile pigment (the other is named biliverdin), which is produced by the breakdown of the blood pigment hemoglobin. Bilirubin has a yellow-orange color. Bile itself is a greenish-yellow alkaline fluid produced by the liver and stored in the gall-bladder. It assists the digestion and absorption of fats.
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Binary describes something made of two things or two parts. In chemistry, this might mean a substance made of two elements or two compounds.
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Binding refers to the combining or uniting of molecules by employing reactive groups within the molecule or by using a binding chemical. Binding is especially associated with a chemical bond that is easily broken.
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Bioassay is a technique used to determine the potency or concentration of a substance (such as a drug) by comparing its effect on a test organism with that of a standard preparation.
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Bioavailability is the degree to which an agent, such as a drug or nutrient, becomes available at the site of activity in the body.
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Biochemical refers to the chemical reactions that occur within a living organism. An example of the chemical reactions includes enzymes that breakdown or build biological molecules.
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Biochemistry is the study of the chemistry of living organisms, especially the structure and function of their chemical components (principally proteins, carbohydrates, lipids, and nucleic acids).
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Biocompatibility is the ability of biologic materials to exist or perform in harmonious combination.
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Biofeedback is the giving of immediate information to a subject about his bodily processes (such as heart rate), which are usually unconscious. In biofeedback, the subject is able to control those processes through training and practice. Biofeedback is an experimental treatment for disturbances of bodily regulation, such as hypertension. Biofeedback is mostly effective for treating high blood pressure, migraine, and epilepsy.
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Bioinstrumentation is the use of a sensor or other device (bioinstrument) to record and transmit physiologic data to a receiving and monitoring station. The device is attached to or embedded in the subject’s body.
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A biologically active molecule has a unique structure that allows it to participate in biochemical reactions.
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Biomass is the total mass of all the organisms of a given type and/or in a given area. It is normally measured in terms of grams of dry mass per square meter.
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Biomechanics is the application of the principles of mechanics to living systems, particularly those living systems that have coordinated movements.
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A biopsy is the process of removing a small section of tissue from a potentially diseased organ or tissue in a living organism. The biopsy sample can undergo more detailed diagnostic examinations like microscopic analysis.
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Biorack is the name for a multipurpose facility designed by the European Space Agency (ESA) to study the effects of microgravity and cosmic radiation on small life forms such as cells, tissue samples, small organisms and plants. Biorack contains three incubators which operate at different temperatures, a cooler, and a freezer, and two 1g reference centrifuges. Biorack was previously flown on STS-61A (D-1), STS-42 (IML-1), STS-65 (IML-2), and STS-76 (Third Mir docking mission).
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Bioregeneration is the renewing or restoring of life-supporting resources using biological processes; usually describing processes in a closed system.
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Bioregenerative systems renew or restore life-supporting resources using biological processes.
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Biorhythms are roughly periodic changes in the behavior or physiology of an organism that is maintained and generated by a biological clock. Well known examples are the sleep cycle, annual rhythms, or menstrual cycles.
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A biosensor is a device which translates biological variables such as electric potentials, movement, chemical concentrations, etc. into electrical signals.
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The biosphere is the whole region of the Earth's surface, including the sea and the air, that is inhabited by living organisms.
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The Biostack is made up of cylindrical containers with layers of dormant biological objects, such as seeds, interleaved with sheets of light or radiation particle detectors. The biological objects identify the biological damage of light or radiation, while the detector sheets map the location of the hit and the size of light particles.
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Biotechnology refers to the industry that uses biological processes to make a product, such as a drug. An example is the use of yeast in the fermentation of beer.
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A blastoid is a cell that has undergone blastogenesis which is the transformation of a functionally dormant cell to an active cell. A blastoid cell is characterized by expansion of the cytoplasm and enlargement of the cell nucleus.
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Blood pressure is the pressure exerted by the flow of blood through the arteries of the body. This pressure is greatest during the contraction of the ventricles of the heart (systolic pressure), which forces blood into the arterial system. Pressure falls to its lowest level when the heart is filling with blood (diastolic pressure).
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Blood Urea Nitrogen (BUN) is nitrogen in the blood in the form of urea. The urea is formed in the liver as the end product of protein metabolism and is deposited in the blood to be excreted through the kidneys. the BUN, determined by blood test, is directly related to the metabolic function of the liver and the excretory function of the kidney.
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Blood volume is the total amount of circulating blood in the body, normally about 5.5 liters.
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The body axis is an imaginary longitudinal line through the vertical center of the body (head to feet) or one of its parts, or a line about which the body or a part rotates. Development of the body in vertebrates and most other animals occurs in a nearly symmetrical fashion around the body axis.
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Bomb calorimetry is a method that uses an instrument for determining the potential energy of organic substances, including those in foods. It consists of a hollow steel container, lined with platinum and filled with pure oxygen, into which a weighed quantity of food is placed and ignited with an electric fuse; the heat produced is absorbed by water surrounding the bomb and, from the rise in temperature, the calories liberated are calculated.
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Bone physiology, or bone and calcium physiology as it's also known, is the study of the structure, processes and function of bone and its major constituent, calcium.
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Bone demineralization is the loss of minerals, such as calcium, from the bone.
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Bone density is the mass per unit volume of bone under specified conditions of pressure and temperature.
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Bone formation is the process by which new bone is created from cells known as osteoblasts or bone forming cells. Bone formation adds minerals such as calcium to bone matrix, making it stronger.
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Bone loss is the weakening and destruction of bone, particularly through demineralization. Demineralization is the loss of minerals, such as calcium from the bones or other mineralized structures of the body.
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Bone marrow is the soft tissue contained within the internal cavities of the bones. Bone marrow is a site of blood cell formation, especially in young animals and humans.
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Bone comprises a matrix of collagen fibers (30%) impregnated with bone salts (70%), mostly calcium phosphate and carbonate.
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Bone metabolism descries the process by which bone is destroyed and rebuilt at any given time to keep up its strength.
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Bone mineralization is the process of adding minerals such as calcium and phosphorous to the bone.
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Bone physiology, or bone and calcium physiology as it's also known, is the study of the structure, processes and function of bone and its major constituent, calcium.
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Bone remodeling sites are specific sites located along most of the outer surface of bone where the synthesis and resorption of bone takes place. The sites are regulated by specialized cells which control the synthesis or resorption process. Long bones also have remodeling sites along the inner surface of the bone shaft, adjacent to the bone marrow cavity.
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Bone resorption is the absorption of the bone by large multi-nucleated cells called osteoclasts; resorption occurs normally in very small amounts, but can claim large quantities of bone in circumstances where normal physical weight-bearing stress is absent, such as bed rest or exposure to microgravity. The loss of calcium is associated with resorption of bone.
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Boric Acid is a white, odorless powder or crystalline substance used as a buffer.
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A Boyden chamber is a simple chamber used to test for chemotaxis, especially of leukocytes. Consists of two compartments separated by a millipore filter (3 - 8 micrometer pore size); chemotactic factor is placed in one compartment and the gradient develops across the thickness of the filter (ca 150 micrometer). Cell movement into the filter is measured after an incubation period less than the time taken for the gradient to decay. See also checkerboard assay.
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The brachialis is a muscle that is situated at the front of the upper arm and contracts to flex (lift-up) the forearm; it works against the triceps brachii (lowering the forearm).
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Gamma particles are produced in abundance when high-energy electrons impinge on any material. The electrons are subject to violent collisions, and the photons that result from these collisions are formally called bremsstrahlung radiation, (bremsstrahlung is German for decelerated-radiation). A gamma particle is known by other names, such as X-ray, photons and light. Low-energy forms are called ultraviolet rays, infrared rays, even radio waves. A photon is one of the fundamental particles in nature and it plays an important role in being involved in the interactions between electrons. Photons are the most familiar particles in everyday existence. The light we see, the radiant heat we feel, microwaves to cook with, are all photons of different energies. A gamma is simply a name given to the most energetic of these particles.
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Bronchitis is an acute or chronic inflammation of mucous membranes of the tracheobronchial tree.
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A buffer is a system capable of resisting changes in pH, consisting of a conjugate acid-base pair in which the ratio of proton acceptor to proton donor is near unity.
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Buffy coat is the thin yellow-white layer of leukocytes on top of the mass of red cells when whole blood is centrifuged.
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A bulk solution is a solution that contains protein molecules used to form the protein crystals.
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Buoyancy is the capacity to float in a liquid medium.