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Label (in assays) | The label is an atom or molecule which is attached to either the ligand or binding protein and which, by itself or as part of an enzyme system, is capable of generating a signal which can be quantitated. | |||||||||||||||||||||||||||||
Lability | State of having notable shifts in emotional state (e.g., uncontrolled laughing or crying). | |||||||||||||||||||||||||||||
Lacrimation | The production, secretion, and shedding of tears. From the Indo-European dakru meaning a tear (from a weeping eye) via the Latin lacrima. | |||||||||||||||||||||||||||||
Lacteal | A tiny lymph vessel extending into the core of an intestinal villus and serving as the destination for absorbed chylomicrons. | |||||||||||||||||||||||||||||
Lactobacillus | Type of prebiotic/probiotic found in yogurt and some other dairy products. | |||||||||||||||||||||||||||||
Lactose intolerance | A genetic trait characterized by the absence of the enzyme lactase, which breaks down lactose, the main sugar in milk and other dairy products. | |||||||||||||||||||||||||||||
Lagging strand | A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork. | |||||||||||||||||||||||||||||
Lag phase | During the lag phase, cells increase in size but not in number because they are adapting to a new environment, and, synthesis and repair are taking place. | |||||||||||||||||||||||||||||
Lag screw | A screw inserted across a fracture that provides compression to the fracture. Lag screws can provide static or dynamic compression. The term "lag" refers to the function of a screw. The physical design of the screw, the type of bone the screw is inserted into, and the manner in which it is inserted determine whether a screw functions as a lag screw. In the diaphyses of long bones, cortical screws are used as lag screws while cancellous screws function as lag screws for cancellous bone fractures. | |||||||||||||||||||||||||||||
Lag time | The initial period in a bacterial population life when cells are adjusting to a new environment before commencing growth. | |||||||||||||||||||||||||||||
Landau reflux | An infantile, automatic posture in which the head and trunk extend when the baby is held in a prone position with the examiner's hands under the trunk. | |||||||||||||||||||||||||||||
Language delay | A term used when the normal rate of language development is interrupted, but the developmental sequence remains intact. | |||||||||||||||||||||||||||||
Language disorder | A term used when the sequence of language development is seriously disrupted. | |||||||||||||||||||||||||||||
Lagrangian Measurement | Measurement of the motion of a fluid by tracing the path traveled by that fluid. | |||||||||||||||||||||||||||||
Large for gestational age (LGA) | When the weight of a newborn is greater than the 90th percentile acceptable norms for the particular gestational age. | |||||||||||||||||||||||||||||
Large intestine | The region of the digestive system after the small intestine and ending in the anal canal that voids through the anus.
The functions of the large intestine include
(see Small Intestine) | |||||||||||||||||||||||||||||
Larva (plural Larvae) | A free-living, sexually immature form in some animal life cycles that may differ from the adult in morphology, nutrition, and habitat. | |||||||||||||||||||||||||||||
Laryngeal webbing | When a membrane grows between the true vocal cords. | |||||||||||||||||||||||||||||
Laryngoscopy | Visual examination of the inside of the larynx to detect tumors, foreign bodies, nerve or structural injury, or other abnormalities. | |||||||||||||||||||||||||||||
Latent heat | The amount of energy required to change a solid to a liquid or liquid to a gas. | |||||||||||||||||||||||||||||
Latent schizophrenia | Having clear symptoms of schizophrenia, but no history of psychotic schizophrenic episodes. | |||||||||||||||||||||||||||||
Lateral line system | A mechanoreceptor system consisting of a series of pores and receptor units (neuromasts) along the sides of the body of fishes and aquatic amphibians. | |||||||||||||||||||||||||||||
Lateral ventricle | One of the fluid filled spaces inside the brain, containing cerebrospinal fluid that acts to cushion the brain. | |||||||||||||||||||||||||||||
Latin square design | A randomisation schedule for drug tests in which each animal receives each treatment once, in a predetermined random sequence. Also used in randomising doses in some isolated tissue experiments. An example for four drugs (A,B,C,D) in a four-day study is shown below.
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Latus rectum | The chord through a focus of an ellipse perpendicular to the major axis. | |||||||||||||||||||||||||||||
Law of independent assortment | Mendel's second law, stating that each allele pair segregates independently during gamete formation; applies when genes for two traits are located on different pairs of homologous chromosomes. | |||||||||||||||||||||||||||||
Law of segregation | Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form pairs during the fusion of gametes at fertilization. | |||||||||||||||||||||||||||||
Laws of Themodynamics | Two laws that govern the flow of energy. | |||||||||||||||||||||||||||||
Laws of Trignometry | Law of cosines: c2 = a2 + b2 - 2abCosC | |||||||||||||||||||||||||||||
L-carnitine | Non-essential amino acid that permits the passage of fatty acids into the mitochondria | |||||||||||||||||||||||||||||
LC50 (LC50 ) | The concentration of air contaminant that will kill 50% of the test animals in a group during a single exposure (inhalation exposure). Generally expressed in units of parts per million or mg of contaminant m3 of air. | |||||||||||||||||||||||||||||
LD50 (LD50 ) | The LD50 value is the quantity of chemical that is lethal to 50% of the tested animals and is usually expressed as the dose in milligrams, per kilogram of the animal’s body weight. The animal species is given, as is the administration route. | |||||||||||||||||||||||||||||
Leading strand | The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction. | |||||||||||||||||||||||||||||
Leak channels or passive channels | Ion channels that are always open in a cell membrane, thereby allowing the movement of the appropriate ion(s) down their concentration gradients. | |||||||||||||||||||||||||||||
Lean body mass | The mass of the body minus the fat: heterogeneous mass composed of body water (> 70 % of the total), muscle proteins and constituents of the skeleton. | |||||||||||||||||||||||||||||
Leaching | the process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals or contaminants, are washed into a lower layer of soil or are dissolved and carried away by water. | |||||||||||||||||||||||||||||
Learning | The process that leads to modification in individual behavior as the result of experience. | |||||||||||||||||||||||||||||
Learning disability (LD) | A disorder in one or more of the basic psychological processes involved in understanding or using language, spoken or written, which may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or do mathematical calculations. The term includes, but is not limited to conditions such as perceptual handicaps, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. The term does not include children who have learning problems which are primarily the result of visual, hearing, or motor handicaps; mental retardation; emotional disturbance; or environmental, cultural, or economic disadvantages. | |||||||||||||||||||||||||||||
Least common denominator | The least common denominator of two fractions, a/b and c/d, is the smallest number that contains both b and d as factors. | |||||||||||||||||||||||||||||
Least common multiple | The least common multiple of two numbers, a and b, is the smallest number that contains both a and b as factors. | |||||||||||||||||||||||||||||
Lecithin | Phosphatides naturally occurring in oil from both plants and animals; A major component of cell membranes containing equal amounts of saturated and monounsaturated fatty acids, phosphate, and choline. Lecithin is a member of the lipid group called phospholipids. Its biochemical name is phosphatidylcholine (PC). Lecithin is capable of forming colloidal solutions in water and possesses emulsifying, wetting and antioxidant properties. | |||||||||||||||||||||||||||||
Leg Bag | A small, thick plastic bag that can be tied to the leg and collects urine. It is connected by tubing to a catheter inserted into the urinary bladder. | |||||||||||||||||||||||||||||
Legionella | Fastidious gram-negative rod is isolated from surface water, mud, and thermallypolluted lakes and streams. There is no known soil or animal source. It is pathogenic for humans, causing pneumonia (Legionnaires disease) or a mild, febrile disease (Pontiac fever). | |||||||||||||||||||||||||||||
Lemma | Atheorem that is proved mainly as an aid in proving another theorem. | |||||||||||||||||||||||||||||
lens | a transparent, colorless, firm structure of the eye, enclosed in a capsule, located between the iris and the vitreous humor; refracts light to focus images onto the retina at the back of the eye; in old age the lens becomes flattened, more dense, slightly opaque, and amber-tinted. | |||||||||||||||||||||||||||||
Lentic water | ponds or lakes (standing water). | |||||||||||||||||||||||||||||
Leptin | A hormone produced mainly by the fat cells of the adipose tissue in the body, that helps regulate food intake, metabolism and reproduction. Leptin has also been shown to promote and sustain the bodys immune response by binding to T lymphocytes. In this regard it appears to actively contribute to the pathogenesis of experimental autoimmune encephalomyelitis (EAE) in mice, influencing both its onset and clinical severity, a disease that is being used as a model of human multiple sclerosis (MS). MS is characterized by the production of autoreactive T lymphocytes that turn against the body and attack cells within the brain and spinal cord, first inducing weight loss and ultimately resulting in paralysis. | |||||||||||||||||||||||||||||
Leptokurtic Distribution | A leptokurtic distribution is a gaussian distribution having a positive kurtosis and a narrow shaped peakedness. | |||||||||||||||||||||||||||||
Leptons | Fundamental particles that are relatively non-reactive and capable of an independent existence: electrons, muons, tau particles and neutrinos. | |||||||||||||||||||||||||||||
Leucine zipper | A motif found in certain proteins in which Leu residues are evenly spaced through an -helical region, such that they would end up on the same face of the helix. | |||||||||||||||||||||||||||||
Leukocyte | A white blood cell, an important component of the body's immune system, such as , such as in phagocytosis or antibody production.. | |||||||||||||||||||||||||||||
Leukemia | A condition in which there is an abnormal increase in the number of white blood cells present in the blood. | |||||||||||||||||||||||||||||
Leukotomy | The operation of cutting the white matter in the oval center of the frontal lobe of the brainAlso known as Lobotomy. | |||||||||||||||||||||||||||||
Leukotrienes | A type of prostaglandin produced by various white blood cells involved in the inflammatory and immune responses and in allergic reactions. | |||||||||||||||||||||||||||||
Leuprolide Stim Test | Specialized blood test used for diagnosing early or delayed puberty.A leuprolide stimulation test is done to determine a child's stage of puberty. The test may be done when it is suspected that a child may soon be entering puberty, or when a child has late puberty. The leuprolide stim test is done by placing an IV catheter in a vein and drawing a small amount of blood to measure hormone levels. Then a medication called Leuprolide Acetate is given by injection into the fatty tissue just under the skin. Blood is drawn 1-3 times after the medication is given to measure hormone levels again. The IV catheter is then removed and the child goes home. Placement of the IV catheter and the injection of medication is slightly painful, but is done quickly. | |||||||||||||||||||||||||||||
Levee | a natural or manmade earthen barrier along the edge of a stream, lake, or river. Land alongside rivers can be protected from flooding by levees. | |||||||||||||||||||||||||||||
Lever | Rigid structure that moves at a fixed point called the fulcrum; | |||||||||||||||||||||||||||||
Library | A library might be either a genomic library, or a cDNA library. In either case, the library is just a tube carrying an unordered mixture of thousands of different clones - bacteria or l phages. Each clone carries an "insert" - the cloned DNA from a particular organism. The relationship of the clones to each other can be established by physical mapping. | |||||||||||||||||||||||||||||
Life cycle | The entire sequence of stages in the life of an organisms, from the adults of one generation to the adults of the next. | |||||||||||||||||||||||||||||
Life-history pattern | A group of traits, such as size and number of offspring, length of maturation, age at first reproduction, and the number of times reproduction occurs, that affect reproduction, survival, and the rate of population growth. | |||||||||||||||||||||||||||||
Life-table | A table of data summarizing mortality in a population. | |||||||||||||||||||||||||||||
Ligaments | A type of fibrous connective tissue that joins bones together at joints. | |||||||||||||||||||||||||||||
Ligand | A ligand is a substance which is capable of binding specifically and reversibly with a binder; The molecule which binds to a protein molecule such as a receptor size, on another molecule. As a ligand binds through the interaction of many weak, noncovalent bonds formed to the binding site of a protein, the tight binding of a ligand depends upon a precise fit to the surface-exposed amino acid residues on the protein. A ligand is termed an antigen when the binder is an antibody. | |||||||||||||||||||||||||||||
Ligand excess | Ligand excess is the presence of excess ligand, in relation to the binder concentration. Severe ligand excess can result in increased solubility of ligand-binder complexes, decreased apparent reactivity, and underestimation of the ligand quantity | |||||||||||||||||||||||||||||
Ligand-gated ion channel receptor | A signal receptor protein in a cell membrane that can act as a channel for the passage of a specific ion across the membrane. When activated by a signal molecule, the receptor either allows or blocks passage of the ion, resulting in a change in ion concentration that usually affects cell functioning. | |||||||||||||||||||||||||||||
Ligase | An enzyme, T4 DNA ligase, which can link pieces of DNA together. | |||||||||||||||||||||||||||||
Ligation | The process of splicing two pieces of DNA together. In practice, a pool of DNA fragments are treated with ligase (see Ligase) in the presence of ATP, and all possible splicing products are produced, including circularized forms and end-to-end ligation of 2, 3 or more pieces. Usually, only some of these products are useful, and the investigator must have some way of selecting the desirable ones. | |||||||||||||||||||||||||||||
Lignans | Type of phytoestrogen found in flax, rye and various vegetables. May lower LDL cholesterol, total cholesterol and triglycerides thereby protecting against heart disease and some cancers. | |||||||||||||||||||||||||||||
Light | The visible part of the electromagnetic spectrum: red, orange, yellow, green, blue, indigo and violet. | |||||||||||||||||||||||||||||
Lightening | a powerful flash of electricity between the negative electrical charges in clouds or between a cloud and the ground. | |||||||||||||||||||||||||||||
Light-dependent reactions | The reactions of the first stage of photosynthesis, in which light energy is captured by chlorophyll molecules and converted to chemical energy stored in ATP and NADPH molecules. | |||||||||||||||||||||||||||||
Light-independent reactions | The carbon-fixing reactions of the second stage of photosynthesis; energy stored in ATP and NADPH by the light-dependent reactions is used to reduce carbon from carbon dioxide to simple sugars; light is not required for these reactions. | |||||||||||||||||||||||||||||
Light microscope | An optical instrument with lenses that refract (bend) visible light to magnify images of specimens. | |||||||||||||||||||||||||||||
Light reactions | The steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process. | |||||||||||||||||||||||||||||
Like terms | Two terms each of whose parts, with the exception of their coefficients, is the same. | |||||||||||||||||||||||||||||
Limbic system | A group of nuclei (clusters of nerve cell bodies) in the lower part of the mammalian forebrain that interact with the cerebral cortex in determining emotions; includes the hippocampus and the amygdala. | |||||||||||||||||||||||||||||
Line | A straight set of points that extends off into infinity in both directions. | |||||||||||||||||||||||||||||
Linea alba (white line) | Tendinous band that runs along the midline of the rectus abdominis. | |||||||||||||||||||||||||||||
Lineage | Any continuous line of descent; any series of organisms connected by reproduction by parent of offspring. A group of organisms, cells, or genes linked to one another through a continuous line of descent, i.e., through parent-offspring connections. | |||||||||||||||||||||||||||||
Linear Regression Coefficients | A least squares linear regression is a model based equation which describes a straight line. It is defined with two coefficients. Coefficient a is the y-intercept; the point on the y-axis that the line intersects. Coefficient b is the slope of the line. | |||||||||||||||||||||||||||||
Linear Binding Region | The linear binding region of an immunoassay standard curve is any region (usually midrange) which appears linear when the standard responses are plotted against their respective concentrations. The length of this region is only a portion of the usable concentration range of the test method and the length of this region (if present) varies among test methods. A linear binding region apparent in an immunoassay standard is not due to any fundamental relationships like the spectral properties of substances in the Beer-Lambert Law. | |||||||||||||||||||||||||||||
Line scale | Unstructured scale usually drawn as a line for marking a decision. | |||||||||||||||||||||||||||||
Line segment | Two points on a line, and all the points between those two points. | |||||||||||||||||||||||||||||
Lineweaver-Burk plot (Also “double reciprocal plot”) | In biochemistry, a graphical representation of the Lineweaver-Burk equation of enzyme kinetics. Taking the reciprocal gives ![]() where V is the reaction velocity, Km is the Michaelis-Menten constant, Vmax is the maximum reaction velocity, and [S] is the substrate concentration. The double reciprocal plot distorts the error structure of the data, and it is therefore unreliable for the determination of enzyme kinetic parameters. Although it is still used for representation of kinetic data, non-linear regression or alternative linear forms of the Michaelis-Menten equation such as the Eadie-Hofstee plot are generally used for the calculation of parameters. When used for determining the type of enzyme inhibition, the Lineweaver-Burk plot can distinguish competitive, noncompetitive and uncompetitive inhibitors. Competitive inhibitors have the same y-intercept as uninhibited enzyme (since Vmax is unaffected by competitive inhibitors the inverse of Vmax also doesn't change) but there are different slopes and x-intercepts between the two data sets. Noncompetitive inhibition produces plots with the same x-intercept as uninhibited enzyme (Km is unaffected) but different slopes and y-intercepts. Uncompetitive inhibition causes different intercepts on both the y and x axes but the same slope. | |||||||||||||||||||||||||||||
Linkage | The tendency for certain alleles to be inherited together because they are located on the same chromosome; The proximity of two or more markers (e.g., genes, RFLP markers) on a chromosome. | |||||||||||||||||||||||||||||
Linkage group | A pair of homologous chromosomes. | |||||||||||||||||||||||||||||
Linkage map | A map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together (i.e., based on the frequencies of recombination between markers during crossing over of homologous chromosomes). The greater the frequency of recombination between two genetic markers, the farther apart they are assumed to be. Distance is measured in centimorgans (cM). | |||||||||||||||||||||||||||||
Linked genes | Genes that are located on the same chromosome. | |||||||||||||||||||||||||||||
Linker | A small piece of synthetic double-stranded DNA which contains something useful, such as a restriction site. A linker might be ligated onto the end of another piece of DNA to provide a desired restriction site. | |||||||||||||||||||||||||||||
Lipid | One of a family of compounds, including fats, phospholipids, and steroids, that are insoluble in water.A lipid is a water insoluble (hydrophobic) substance and is the name of a large class of structurally and functionally diverse molecules. Important lipids include fatty acids (saturated and unsaturated), they are a component of phospholipids and fats | |||||||||||||||||||||||||||||
Lipoprotein | A protein bonded to a lipid.This includes the low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs) that transport fats and cholesterol in blood. These are protein based carriers of triglycerides (fats) and cholesterol in the blood circulation. The low-density lipoprotein particle LDL is also known as 'bad cholesterol' as it is the major carrier of blood plasma cholesterol and high levels of LDL particles are associated to increased risk of heart disease. | |||||||||||||||||||||||||||||
Liposomes | Small lipid particles that can be absorbed into skin. | |||||||||||||||||||||||||||||
Liquid Chromatography Mass Spectrometry (LC-MS) | A technique that combines the physical separation capabilities of liquid chromatography (see Chromatography) (or HPLC) with the mass analysis capabilities of mass spectrometry. | |||||||||||||||||||||||||||||
Liquid crystal display | Thin, flat, and low-power device made up of coloured pixels arrayed in front of a light source (or reflector). | |||||||||||||||||||||||||||||
Lissencephalic | When the telencephalic hemispheres (i.e. cerebral cortex) are relatively smooth (as opposed to "gyrencephalic" when the cortex is highly folded). | |||||||||||||||||||||||||||||
Listeria | Listeria monocytogenes is a Gram-positive bacterium, found in at least 37 mammalian species, as well as 17 species of birds and possibly some fish and shellfish. The bacteria can be isolated from soil, and is resistant to heat, freezing and drying. Listeria has been associated with foods such as raw milk, soft-ripened cheeses, ice cream, raw vegetables, raw and cooked poultry, raw meat and raw and smoked fish. Unlike other pathogenic bacteria, such as salmonella, listeria can survive and grow at temperatures as low as 5°C (41°F). | |||||||||||||||||||||||||||||
Lithotripsy or Nephrolithotripsy | Crushing kidney stones with sound waves. The crushed material from crushing kidney stones has an easy direct pathway out of the body (down the ureter to the bladder and out the urethra). Nephrolithotripsy is an elective procedure that may spare a patient surgery. | |||||||||||||||||||||||||||||
Live gate | Gate through which any data from the flow cytometer/computer parallel interface must pass before acquisition. Any data outside the gate does not enter the computer. | |||||||||||||||||||||||||||||
Livestock water use | water used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs. | |||||||||||||||||||||||||||||
Living modified organism | Any organism in which the genetic material [including both DNA and RNA] has been altered in a way that does not occur naturally by mating and/or natural recombination.Any organism or part thereof which is capable of regenerating itself on its own or in the body or cell of another organism and whose genetic material has been modified by modern biotechnology in a way which does not occur naturally by mating or recombination, [or any living organism or part thereof which had been a fossil but has been resuscitated through modern biotechnology]. These include subcellular particles such as plasmids, DNA fragments and vectors. | |||||||||||||||||||||||||||||
Local optimum | A solution to a problem that is better than all other solutions that are slightly different, but worse than the global optimum. | |||||||||||||||||||||||||||||
Locked-in Syndrome | A condition resulting from interruption of motor pathways in the ventral pons, usually by infarction.This disconnection of the motor cells in the lower brain stem and spinal cord from controlling signals issued by the brain leaves the patient completely paralyzed and mute, but able to receive and understand sensory stimuli; communication may be possible by code using blinking, or movements of the jaw or eyes, which can be spared. | |||||||||||||||||||||||||||||
Loculus | A small cavity or hollow space within an organism or in an organ. Also locules, loculi, locular, locule. | |||||||||||||||||||||||||||||
Locus (in DNA) | The position on a chromosome of a gene or other chromosome marker; also, the DNA at that position. The use of locus is sometimes restricted to mean regions of DNA that are expressed (see gene expression). | |||||||||||||||||||||||||||||
cLog P | Calculated log P (i.e. a theoretical value). | |||||||||||||||||||||||||||||
Log D | Log P when the test is performed at pH 7.4. | |||||||||||||||||||||||||||||
Log P | A measure of the lipophilicity of a compound; its partition coefficient between an organic solvent (usually octanol) and an aqueous buffer. Conc. of non-ionised drug in buffer Values usually range from -6 to +6, high positive values indicating high lipid solubility and low or negative values indicating hydrophilic compounds. The test is performed at a pH at which the compound is non-ionised (compare Log D). | |||||||||||||||||||||||||||||
Logarithm | if y = bx, then logb y = x. | |||||||||||||||||||||||||||||
Logistic | A five parameter logistic curve is a model based equation which describes a nonlinear curve such as that found with most immunoassay standard curves and in many biological ractions/relationships. | |||||||||||||||||||||||||||||
Logistic population growth | A model describing population growth that levels off as population size approaches carrying capacity. | |||||||||||||||||||||||||||||
Logit | The logit transform is a transformation which stretches the interval between successive responses of sample concentration logarithms disproportionally at the two asymptotic ends of the standard curve and makes the standard curve more linear. A logit transform also disproportionally increases the heteroscedasticity at the two asymptotes. | |||||||||||||||||||||||||||||
Longitudinal study | In survey research, a study in which a panel of individuals is interviewed repeatedly over a period of time once. Contrast with cross sectional studies in which. data are obtained only . | |||||||||||||||||||||||||||||
Long latency or transcortical reflexes | The delayed and smaller electromyographic changes that are seen following the sudden stretch of a muscle. The dorsal column-medial lemniscal system and corticospinal tract are thought to relay the afferent and efferent limbs of this reflex, which may have a role in load compensation. | |||||||||||||||||||||||||||||
Long-term self-renewal | The ability of stem cells to replicate themselves by dividing into the same non-specialized cell type over long periods (many months to years) depending on the specific type of stem cell. | |||||||||||||||||||||||||||||
Loop of Henle | The long hairpin turn, with a descending and ascending limb, of the renal tubule in the vertebrate kidney; functions in water and salt reabsorption. | |||||||||||||||||||||||||||||
Loosening of associations | Thinking characterized by speech in which ideas shift from one subject to another that is completely unrelated or only obliquely related, without the speaker's showing any awareness that the topics are unconnected. | |||||||||||||||||||||||||||||
Lorica | A vase-shaped or cup-shaped outer covering. | |||||||||||||||||||||||||||||
Lotic water | flowing waters, as in streams and rivers. | |||||||||||||||||||||||||||||
Lower motoneuron | Lower motoneurons are those motorneurons that directly innervate the skeletal muscles. LMNs are found in some of the cranial nerve nuclei in the brainstem as well as in Layer X in the ventral (anterior) horn of the spinal cord. | |||||||||||||||||||||||||||||
Lower motoneuron syndrome | A group of symptoms resulting from disease of either the motoneuron or the muscle or both. Damage to the LMN results in muscle weakness, wasting with a loss of reflexes, more specifically in flaccid paralysis, lack of muscle tone and reflexes, muscle atrophy, and (initially) muscle fasciculations (small, uncoordinated muscle fiber contractions) | |||||||||||||||||||||||||||||
Lowest Specific Binding | The lowest specific binding (LSB) standard is the standard expected to yield the lowest bound response. The LSB is used to calculate one of the method control monitor points in the absence of the appropriate baseline standard. In competitive binding assays, the highest concentration standard is the LSB. In sandwich binding assays, the lowest concentration standard is the LSB. | |||||||||||||||||||||||||||||
Low back pain | Pain in the lower back area that can relate to problems with the lumbar spine , the discs between the vertebrae , the ligaments around the spine and discs, the spinal cord and nerves , muscles of the low back, internal organs of the pelvis and abdomen , or the skin covering the lumbar area. | |||||||||||||||||||||||||||||
Low tone hypotonic | Having poor muscle tone, appearing floppy. | |||||||||||||||||||||||||||||
Lumbar (spinal) puncture or tap (LP) | A technique to sample the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. | |||||||||||||||||||||||||||||
Lumen | The cavity of a tubular structure, such as endoplasmic reticulum or a blood vessel. | |||||||||||||||||||||||||||||
Lumpectomy | Surgery to remove abnormal tissue or cancer from the breast and a small amount of normal tissue around it. It is a type of breast-sparing surgery. | |||||||||||||||||||||||||||||
Lung | The invaginated respiratory surfaces of terrestrial vertebrates, land snails, and spiders that connect to the atmosphere by narrow tubes. | |||||||||||||||||||||||||||||
Lung cancer | Malignancy of the lung tissue. | |||||||||||||||||||||||||||||
Lung compliance | The change in lung volume per unit pressure change | |||||||||||||||||||||||||||||
Lutein | Type of carotenoid found in most green vegetables. Positively contributes to maintenance of eye vision. | |||||||||||||||||||||||||||||
Lutenising hormone (LH) | A gonadotropin (hormone from the pituitary gland) that stimulates the ovaries or testes. A protein hormone secreted by the anterior pituitary that stimulates ovulation in females and androgen production in males. | |||||||||||||||||||||||||||||
Lycopene | Carotenoid related to the better known beta-carotene. | |||||||||||||||||||||||||||||
Lymph | A clear fluid, derived from interstitial fluid, that travels through the lymphatic system. It carries cells that help fight infections and other diseases. Also called lymphatic fluid. | |||||||||||||||||||||||||||||
Lymphokines | Peptides and proteins secreted by (immune system response) stimulated T cells. | |||||||||||||||||||||||||||||
Lymph node | A rounded mass of spongy lymphatic tissue that is surrounded by a capsule of connective tissue. Lymph nodes are located throughout the lymphatic system. They remove filter lymph (lymphatic fluid) to remove dead cells, debris, and foreign particles from the circulation. They also store lymphocytes (white blood cells) and are sites at which foreign antigens are displayed to immunologically active cells. | |||||||||||||||||||||||||||||
Lymphatic circulation | The circulation of the lymphatic system, which is part of the immune system. | |||||||||||||||||||||||||||||
Lymphatic system | A network of glands and vessels that drain interstitial fluid from body tissues and return it to the circulatory system. | |||||||||||||||||||||||||||||
Lymphocyte | A type of leukocyte (white blood cell) found in the blood, lymph nodes and certain organs. Lymphocytes are continuously made in the bone marrow. The lymphocytes that complete their development in the bone marrow are called B cells, and those that mature in the thymus are called T cells. (see also B lymphocytes and T lymphocytes). | |||||||||||||||||||||||||||||
Lysis | Disintegration of a cell by rupture of its plasma membrane. | |||||||||||||||||||||||||||||
Lysogenic bacteria | Bacteria carrying a bacteriophage integrated into the bacterial chromosome. | |||||||||||||||||||||||||||||
Lysogenic cycle | A type of phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage. | |||||||||||||||||||||||||||||
Lysosome / Lyzosome | A membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.Eukaryotic organelle which carries digestive enzymes. The lyzosome fuses with a vacuolar membrane containing ingested particles, which are then acted upon by the enzymes. | |||||||||||||||||||||||||||||
Lysozyme | An enzyme in perspiration, tears, and saliva that attacks bacterial cell walls. | |||||||||||||||||||||||||||||
Lytic cycle | A type of viral replication cycle resulting in the release of new phages by death or lysis of the host cell. |