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Babinski reflex

Extension of the great toe with fanning of the other toes on stimulation of the sole of the foot. May be indicative of a lesion involving the pyramidal tract

Bacillus (plural = Bacilli)

A rod-shaped bacterium.


The cross of an individual with one of its parents or an organism with the same genotype as a parent.

Background (in  assays)

Background samples are instrument blanks which measure the amount of the raw response which is due to residual activity from the detector. This residual activity can be from instrument noise, extraneous radiation, and other artifacts. The average of the background sample raw responses is subtracted from all sample raw responses prior to all subsequent calculations. The raw response which is stored in test data includes the background average response

Back mutation

A change in a nucleotide pair in a mutant gene that causes reversion, i.e., restores the original sequence and hence the original phenotype.


Single cell organisms and most prevalent form of life on Earth; Large and diverse group of single-celled micro-organisms lacking a nucleus.
Bacteria are also known as prokaryotes (together with archaea; formerly archaebacteria) referring to the single compartment inside the cell and missing a membrane delineated cell nucleus found in all eukaryotes. Reproduce by division. Bacteria are found in all habitats, both in the environment and within the bodies of the largest organisms. Can be both harmful and helpful to human health. Examples are Escherichia coli (E.coli), Salmonella typhimurium (S. typhi), Mycobacterium tuberculosis (M. tuberculosis), or Helicobacter pylori (H. pylori).

Bacterial artificial chromosome (BAC)

vector (or cloning vehicle) used to clone DNA fragments of 100 to 300 kilobases (kb) of target sequence (insert size), with an average of 150 kb,  in cells of the Escherichia coli (a type of basterium). Based on the naturally occurring F-factor plasmid found in the bacterium Escherichia coli. They are propagated as a mini-chromosome in a bacterial host. The size of the typical BAC is ideal for use as an intermediate in large-scale genome sequencing projects. Entire genomes can be cloned into BAC libraries, and entire BAC clones can be shotgun-sequenced fairly rapidly.

Bacterial growth phases

Can exhibit at least four different phases: lag phase, growth phase, stationary phase and death phase.

Bacterial meningitis

An inflammation of the meninges (membranes in the brain or spinal cord) caused by bacterial infection.

Bacterial strain

Population of bacterial cells all descended from a single pure isolate.


A class of antibiotics that kills bacterial cells.


Small, naturally occurring protein produced by one species of bacterium that effectively protects it from competing organisms.
Different bacteria produce different bacteriocins.


A type of virus that attacks bacteria. (Also called phage)
Bacteriophages consist of protein coats covering DNA. They infect a cell by injecting DNA into the host cell. This viral DNA then "disappears" while taking over the bacterial machinery and beginning to make new virus instead of new bacteria. After 25 minutes the host cell bursts, releasing hundreds of new bacteriophage. Some phages, however, will incorporate their DNA into that of their host, and remain dormant for an extended period. For this reason, they have become essential tools of genetic engineers. Phages have DNA and protein, making them ideal to resolve the nature of the hereditary material.

Bacteriophage lambda

virus which infects E. coli , and which is often used in molecular genetics experiments as a vector, or cloning vehicle.
Recombinant phages can be made in which certain non-essential  DNA is removed and replaced with the DNA of interest. The phage can accommodate a DNA "insert" of about 15-20 kb. Replication of that virus will thus replicate the investigator's DNA. One would use phage  rather than a plasmid if the desired piece of DNA is rather large.


A class of antibiotics that prevents growth of bacterial cells.


An organism that eats bacteria.
Hence: Bacterivorous: Said of bacterivores.

Baculovirus Expression Vector System (BEVS)

Refers to an insect cell culture system in which a genetically engineered baculovirus expression vector (BEV) is utilized to carry into the insect cells a gene which codes-for a protein desired by man.


The ability to use appropriate righting and equilibrium reactions to maintain an upright position. It is usually tested in sitting and standing positions.

Balanced lethal system

An arrangement of recessive lethal alleles that maintains a heterozygous chromosome combination.
Homozygotes for any lethal-bearing chromosome perish.

Balanced polymorphism

A type of polymorphism in which the frequencies of the coexisting forms do not change noticeably over many generations.Stable genetic polymorphism maintained by natural selection.

Balling hydrometer scale

A hydrometer scale, devised by J N Balling, calibrated so that readings at a specified temperature (usually 20°C) equal the percentage by weight of sugar in the solution.
It is numerically equivalent to the Brix hydrometer scale, but is chiefly used by brewers, whereas the Brix scale is used by sugar refineries and vintners.

Ballism or Ballismus

Basal ganglion disease characterized by violent flinging movements of the limbs due to contraction of proximal limb muscles.Wide flinging or jerking movements of the extremities.

Balloon angioplasty

A procedure to enlarge the opening in a blood vessel that has become narrowed or blocked by plaque.A small balloon is filled with air inside the blood vessel to push the plaque against the blood vessel wall and increase the opening.

Baltimore Classification of Viruses

A classification system of viruses based on genetic contents and replication strategies of viruses. 
The genetic material in all types of cells is double-stranded DNA, but some viruses use RNA or single-stranded DNA to carry genetic information.
According to this classification, viruses are divided into the following seven classes:

  • dsDNA viruses
  • ssDNA viruses
  • dsRNA viruses
  • (+)-sense ssRNA viruses
  • (-)-sense ssRNA viruses
  • RNA reverse transcribing viruses
  • DNA reverse transcribing viruses

where "ds" represents "double strand" and "ss" denotes "single strand".


A group of drugs derived from barbituric acid that is used to sedate, to control convulsions, or to induce sleep.Barbiturates may be habit forming.

Bariatric surgery

Surgery on the stomach and/or intestines to help a person with extreme obesity to lose weight. Bariatric surgery is an option for people who have a body mass index (BMI) above 40. Surgery is also an option for people with a BMI between 35 and 40 who have health problems like type 2 diabetes or heart disease.
There are two main types of bariatric surgery, adjustable gastric banding and gastric bypass.
In adjustable gastric banding, insertion of a band restricts the size of the opening from the esophagus to the stomach. The size of the opening to the stomach determines the amount of food that can be eaten. The size of the opening can be controlled by the surgeon by inflating or deflating the band through a port that is implanted beneath the skin on the abdomen. The band can be  removed at any time.
In contrast to gastric banding, gastric bypass (sometimes referred to as roux-en-Y gastric bypass) is a permanent reduction in the size of the stomach. The proximal portion of the stomach is used to create an egg-sized pouch that is connected to the intestine in a location that bypasses about 2 feet of normal intestine. The amount of food that can be eaten is limited by the size of the pouch and the size of the opening between the pouch and the intestine.

Barr body

A densely staining mass that represents an inactivated X-chromosome in mammalian females. Although inactivated, the Barr body is replicated prior to cell division and thus is passed on to all descendant cells of the embryonic cell that had one of its X-chromosomes inactivated.


a device used to measure the pressure of the atmosphere.  The barometer unit of measure is called millibars.


A three quark hadron.  The most common baryons are protons and neutrons.

Basal body

A structure at the base of a cilium or flagellum.A short cylindrical array of nine triplet microtubules and other proteins arranged in a circle with no central microtubule. Found at the base of a eukaryotic cilium or flagellum.  It organises the assembly of the axoneme (the bundle of microtubules and other proteins forming the core of each cilium or flagellum).

Basal ganglia

A group of nerve cells located at the base of the brain, composed of nuclei called the putamen, caudate, globus pallidus, and substantia nigra. These nerve cells participate in the regulation of motor performance.

Basal group

The earliest diverging group within a clade; for instance, to hypothesize that sponges are basal animals is to suggest that the lineage(s) leading to sponges diverged from the lineage that gave rise to all other animals.

Basal metabolic rate (BMR)

The energy required to keep the body functioning at rest. The minimal number of kilocalories a resting animal requires to fuel itself for a given time. Measured in calories.

Base (with respect to a solution)

See Alkali
Base / Alkali has less free hydrogen ions (H+) than hydroxyl ions (OH-). a bitter tasting substance (and often slimy) - the opposite of a acid substance.  Base solutions will turn a litmus blue.

Base (in genetics)

Nitrogenous molecules that form the building block of the DNA chain. (see Base pair)The four types of bases are adenine (A), guanine (G), thymine (T) and cytosine (C). The bases are the letters of the alphabet in which genetic information is re

Base analogue

A chemical whose molecular structure mimics that of a DNA base.
Because of the similarity, the analogue may act as a mutagen.

Base-ionization constant, Kb

The degree to which a base ionizes; Ka = [X+][OH-] ------ [XOH]

Base flow

Sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced streamflows. Natural base flow is sustained largely by ground-water discharges.

Baseline standards (in assays)

The baseline standards are samples which are used in the mathematical calibration of all samples but are not plotted on the standard curve.Baseline standards include background samples, tracer activity samples, nonspecific binding samples, and maximum binding samples. The last two baseline standards are sometimes used to represent the infinitely low and infinitely high standard concentrations at the two asymptotes.

Basement membrane

The floor of an epithelial membrane on which the basal cells rest.

Base pair (bp)

Two complementary nitrogenous bases in a DNA molecule, such as the nucleotide coupling of adenine with thymine (A:T) and guanine with cytosine (G:C); also, a unit of measurement for DNA sequences; A pair of nucleotides on opposite strands of a nucleic acid hydrogen-bonding with each other according to the pairing rules between a pyrine and a pyrimidine.Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs.
Hence base-pairing principleIn the formation of nucleic acids, the requirement that adenine must always pair with thymine (or uracil) and guanine with cytosine.

Base-pair substitution

A point mutation; the replacement of one nucleotide and its partner from the complementary DNA strand by another pair of nucleotides.

Base sequence

The order of nucleotide bases in a DNA molecule.
Length is usually defined as the number of base pairs.
Hence Base sequence analysis = A method, sometimes automated, for determining the base sequence.

Basic solution

A solution that has a higher concentration of hydroxide ions that hydrogen ions.
The solution has a pH between 7 and 14.

Basilar membrane

The membrane beneath hair cells in the cochlea of the inner ear that vibrates in response to sound.Forms the lower boundary of the middle cochlear compartment, scala media, and thus of the cochlear partition.


A type of white blood cell (leukocyte) produced by stem cells within the bone marrow; that synthesizes and stores histamine and also contains heparin. Also called basophilic leukocytes.When two IgE molecules of the same antibody "dock" at adjacent receptor sites on a basophil cell, the two IgE molecules capture an allergen between them. A chemical signal is sent to the basophil causing the basophil cell to release histamine, serotonin, bradykinin, and "slow-reacting-substance." Release of these chemicals into the body causes the blood vessels to become more permeable which consequently causes the nose to run. These chemicals also cause smooth muscle contraction, resulting in sneezing, coughing, wheezing, etc.

Batesian mimicry

A palatable/harmless mimic resembling an unpalatable/vigilant model; Form of mimicry in which an innocuous mimic species gains protection by resembling noxious or dangerous model species.
Batesian mimicry postulates that palatable mimics are likely to gain protection from predators that have learned to avoid the unpalatable/vigilant model as long as the mimic remains relatively rare compared to the model.


A device that produces electricity by means of chemical reaction.  A battery consist of one or more units called electric cells.  Each cell has all the chemicals and parts needed to produce an electric current.

Batten disease (Also "neuronal ceroid lipofuscinosis" or "NCL")

Gray matter progressive nervous system disease. The child develops normally until 6 months to 2 years and then starts to lose skills. Eventually seizures, mental retardation, and blindness occur.


Baud is the capacity unit for data transmission in communication systems, and expresses information units per second. Each information unit may contain one or more information bitsMost often, used superficially (and incorrectly) to mean bits/second.Modern communication techniques use both amplitude and phase information to code a set of bits into each information unit, like 4800 bits/s on a 1200 baud link. The bandwidth required is given by the baud rate, while the bit/s defines the quality requirements on the link. Use of the latter unit is recommended in most practical contexts.

Bayes Theorem

A theorem concerning conditional probabilities of the form P(A|B) [read: ``the probability of A, given B''].A fundamental theorem of probability theory, but its use in statistics is a subject of some controversy.

Bayesian statistics

An important school of statistical theory, in which statistics is derived from a probability interpretation that includes the degree of belief in a hypothesis. It thus refers not only to repeatable measurements (as does the frequentist interpretation)
What is called a ``Bayesian'' viewpoint is the application of the laws of probability to non-repeatable events: H is a hypothesis or proposition, either true or untrue, and P(H) is interpreted as the degree of belief in the proposition.

Bayley Mental Scale

A testing instrument which assesses cognitive abilities. This scale is designed to "assess sensory-perceptual acuities, discriminations, and the ability to respond to these; the early solving ability; vocalizations and the beginnings of verbal communication and early evidence of the ability to form generalizations and classifications".

B cells

Type of lymphocyte responsible for antibody-mediated immunity.B cells mature in the bone marrow and circulate in the circulatory and lymph systems where they transform into antibody-producing plasma cells when exposed to antigens

Bed rock

The solid rock beneath the soil and superficial rock. A general term for solid rock that lies beneath soil, loose sediments, or other unconsolidated material.

Beer-Lambert Law

An equation which describes the linear relationship between the absorption and the concentration of the absorbing material (absorber). The law states that absorbance (ABS) is equal to absorptivity a, multiplied by the pathlength or the distance the light travels through the sample b, multiplied by the concentration c (ABS= abc)
The law, applied in spectrophotometry, describes the quantitative relationship between the absorbance of radiant energy, the concentration of the sample solution, and the length of the path through the sample.
A = c e l

A = Absorbance
c = Concentration
e = extinction coefficient
l = optical path length (typically 1 cm)


The total collection of actions and reactions exhibited by a person.

Behaviour modification

A technique of changing human behavior based on the theory of operant behavior and conditioning. Careful observation of events preceding and following the behavior in question is required. The environment is manipulated to reinforce the desired responses, thereby bringing about the desired change in behavior.

Behavioral ecology

A heuristic approach based on the expectation that Darwinian fitness (reproductive success) is improved by optimal behavior.

Behavioral observation audiometry (BOA)

The assessment of hearing by noting a child's unconditioned responses, such as eye movements, etc., to sounds presented at measured levels in a sound treated room.

Behavioral play audiometry

The use of games and toys in modified pure tone and speech audiometry testing.

Behind-the-ear hearing aid (BTE)

A hearing aid that hangs behind the ear and usually attaches to a tube leading into the ear canal.

Belching (burping or eructating)

The act of expelling gas from the stomach out through the mouth.
The usual cause of belching is a distended (inflated) stomach that is caused by swallowed air or gas. The distention of the stomach causes abdominal discomfort, and the belching expels the air and relieves the discomfort. The common reasons for swallowing large amounts of air (aerophagia) or gas are gulping food or drink too rapidly, anxiety, and carbonated beverages. People often are unaware that they are swallowing air. Moreover, if there is not excess air in the stomach, the act of belching actually may cause more air to be swallowed. "Burping" infants during bottle or breastfeeding is important in order to expel air in the stomach that has been swallowed with the formula or milk.


Benchmarking (of computers) consists of defining one or several variables that describe a computer system's performance, and to measure these variables.
There is no standard or generally accepted measure for computer system capacity: ``capacity'' is a mix of multiple parameters like cycle time, memory access time, architectural peculiarities like parallelism of processors and their communication, instruction parallelism or pipelining, etc. Usually, benchmarks should include system software aspects like compiler efficiency and task scheduling. Potential buyers of computer systems, in particular large and parallel systems, usually have to go to more or less detailed understanding of systems, and perform benchmark tests, i.e. they execute performance measurements with their own program mix, in order to assess the overall performance of candidate systems.
Attempts to express computer capacity in a single or a few numbers have resulted in more or less controversial measures; conscientious manufacturers advertise with several or all of these.
MIPS is an acronym for Million Instructions Per Second, and is one of the measures for the speed of computers. It has been attempted, theoretically, to impose an instruction mix of 70% additions and 30% multiplications (fixed point), and architectural factors as much as efficiency of scheduling or compilation should be entirely ignored. This makes the measure a simple and crude one, barely superior to cycle time. In practice, vendors usually make some corrections for such factors, and the results found are considered more or less controversial. Sometimes a floating point instruction mix is used; the unit is then called MFLOPS, clearly not a useful measure for some types of programs.
The Whetstone benchmark (like a later relative, Dhrystone) is a group of synthetic (i.e. artificially defined) program pieces, meant to represent an instruction mix matching the average frequency of operations and operands of ``typical'' program classes.
A different effort resulted in the SPEC benchmarks: a grouping of major workstation manufacturers called the System Performance Evaluation Cooperative agreed on a set of real programs and inputs, against which to measure performance. Real programs such as a mix of Linpack (linear algebra) operations are also frequently used for benchmarks.

Benign prostatic hypertrophy (BPH)

Swelling of the prostate gland which surrounds the base of the male bladder and urethra causing difficulty urinating, dribbling, and nocturia.
Cured by Transurethral resection of the prostate (TURP) in which an instrument inserted through the penile urethra is used to partially cut away the prostate to relieve obstruction of the urinary tract.


A chemical often used as the active ingredient in mind-affecting drugs such as tranquilizers. Long term use can result in dependence.

Bernoulli effect

Bernoulli's theorem implies that a decrease in fluid pressure is associated with an increase in the fluid's velocity (speed).Described by Swiss mathmetician Daniel Bernoulli in 1738, Bernoulli's theorem (sometimes called the Venturi effect) is the basis for aircraft wing design explaining that air flowing over the upper, curved part of the wing moves faster than the air on the underside of the wing so that the pressure underneath is greater and hence causes lift. - described by Swiss mathmetician Daniel Bernoulli in 1738.  Bernoulli's theorem (sometimes called the Venturi effect) implies that a decrease in fluid pressure is associated with an increase in the fluid's velocity (speed).  It's the basics for aircraft wing design explaining that air flowing over the upper, curved part of the wing moves faster than the air on the underside of the wing so that the pressure underneath is greater and hence causes lift.

Beta amyloid protein

The primary component of plaques which are characteristic pathological features of
Alzheimer’s disease.

Beta blockers

Drugs that act at Beta-adrenergic receptors at the heart to block the action of adrenaline and noradrenaline on the heart. Beta blockers reduce the heart rate and the force of muscle contraction, thereby reducing the oxygen demand of heart muscles.


Orange-coloured plant pigment that can be converted into vitamin A in the human body. Beta-carotene is found in deep-yellow and leafy dark-green vegetables.

Beta decay

Type of radioactive decay in which a radioisotope emits a small, negatively-charged and fast-moving particle from its nucleus. The beta particle is similar in size, charge, and speed to an electron and is formed when a neutron in the radioisotope's nucleus converts to a proton.

Beta galactosidase

The enzyme that splits lactose into glucose and galactose (coded by the gene lac z in the lac operon of Escherichia coli).
Also: Beta-galactosidase acetyltransferase = an enzyme that is involved in lactose metabolism (encoded by the gene lac a in the lac operon of Escherichia coli.
Beta-galactosidase permease = an enzyme involved in concentrating lactose in the cell (coded by the gene lac y in the lac operon of Escherichia coli)).


Soluble fiber in oats.Reduces risk of cardiovascular disease by decreasing circulating blood cholesterol.

Beta oxidation

The process by which fats, in the form of Acyl-CoA molecules, are broken down in the mitochondria to generate Acetyl-CoA, the entry molecule for the Krebs Cycle.

Beta particles

Subatomic particles, essentially electrons, which are emitted during the disintegration of certain radioactive isotopes such as 3H and 14C, which are used as tracers in radioimmunoassays.Beta emitting samples are solubilized in scintillation cocktails containing fluorescent organic compounds and measured in liquid scintillation counters. Many compounds, including water, reduce the fluorescent efficiency by absorbing some of the radiation. This quenching activity can be corrected using quench correction curves or other correction mechanisms. Many liquid scintillation counters automatically correct for quench

Beta-pleated sheet

A regular element of secondary structure in proteins, in which two or more extended strands of the polypeptide chain lie side by side (running either parallel or antiparallel), held together by a regular array of hydrogen bonds between backbone NH and C=O groups, to form a ridged planar surface.
The amino-acid side chains alternately face to opposite sides of the sheet.


Point B is between points A and C if AB + BC = AC.


Abbreviation for base (or biological) equivalent weight. Drug doses are usually expressed in terms of the weight of active substance (usually a base). When a drug salt (e.g. a hydrochloride) or a form which contains water of crystallisation is used, the BEW is the ratio which determines how much salt (or hydrated compound) has to be used to give the desired dose of active drug.

                     Mol. wt. of salt
      BEW =    ----------------------------
                 Mol. wt. of active moeity

B form DNA

A right-handed double-helical conformation of DNA normally seen in solution described by Watson and Crick. A second DNA conformation (A form) is seen in unhydrated DNA (fibres or crystals of oligonucleotides).


Essential for regulating vital functions and one of the important buffers necessary to maintain normal acid-base balance in the body. Body metabolism results in mainly acid production, and neutralizing some of such acids is its constant activity, thus it plays a key role in metabolic acidosis or alkalosis. Bicarbonate may be lost through watery feces, or can decrease when lungs cannot expel carbon dioxide.


Spectrophotometry which uses a secondary wavelength absorbance reading subtracted from a primary wavelength absorbance reading to obtain a delta absorbance reading (Ad). The delta absorbance is used in conjunction with the calibration data to calculate concentration or activity.

Biconditional statement

A compound statement that says one sentence is true if and only if the other sentence is true.


Pertaining to both right and left sides.


A digestive biochemical that emulsifies fats; The digestive juice released from liver (stored in gall bladder) into the digestive tract to help solubilize and absorb fat soluble nutrients.A yellow secretion of the vertebrate liver, temporarily stored in the gallbladder and composed of organic salts that emulsify fats in the small intestine. Bile contains bile acids, biochemical derivatives of cholesterol. Bile acids serve as intestinal detergents for the proper homogenization and uptake (absorption) of dietary lipids.


A yellow pigment produced by the breakdown of red blood cells in the liver. Elevated levels of bilirubin lead to jaundice.


A component of the terpenoids that have been shown to have neuroprotective properties though their role in motor nerve cell regeneration.

Bi-metallic thermometer

Food thermometer used to measure product temperatures. Uses a spring mechanism to determine temperature.

Bimodal Distribution

A distribution with two identifiable foci or modes such that two curves of data distribution can be identified.

Binary fission

The process in which a parent cell splits into two daughter cells of approximately equal size. Simple cell division in single-celled organisms. The type of cell division by which prokaryotes reproduce; each dividing daughter cell receives a copy of the single parental chromosome.

Binary format

Any file format in which information is encoded in some format other than a standard character encoding scheme .A file written in binary format contains information which is not displayable as characters. Software capable of understanding the particular binary format method of encoding information must be used to interpret the information in a binary formatted file. Binary formats are often used to store more information in less space than possible in a character format file. They can also be searched and analyzed more quickly by appropriate software. A file written in binary format could store the number "7" as a binary number (instead of as a character) in as little as 3 bits (i.e., 111), but would more typically use 4 bits (i.e., 0111). Binary formats are not normally portable, however. Software program files are written in binary format. Examples of numeric data files distributed in binary format include: the IBM-binary versions of the Center for Research in Security Prices files, the U.S. Department of Commerce's National Trade Data Bank on CD-ROM . The International Monetary Fund distributes International Financial Statistics in a mixed character-format and binary (packed-decimal ) ) format. SAS and SPSS store their system files in binary format.

Binary number

A number written using binary notation which only uses 0’s and 1’s .
Example: decimal number seven in binary notation is: 111.
The places in the binary numbers are   .......2n.......25 , 24, 23, 22, 21, 20.

Binder (in assays)

A substance which is capable of binding specifically and reversibly with a ligand.
The principal types of binders are antibodies (immunoassays), naturally occurring binding proteins (competitive protein binding assays), and naturally occurring cell receptors (receptor assays).

Binding site

A place on cellular DNA to which a protein (such as a transcription factor) can bind.Typically, binding sites might be found in the vicinity of genes, and would be involved in activating transcription of that gene (promoter elements), in enhancing the transcription of that gene (enhancer elements), or in reducing the transcription of that gene (silencers). Note that whether the protein in fact performs these functions may depend on some condition, such as the presence of a hormone, or the tissue in which the gene is being examined. Binding sites could also be involved in the regulation of chromosome structure or of DNA replication.

Binding type

The binding type is the type of ligand immunoassay technology used in the test method, such as RIA or ELISA.

Binning (of data)

The process of grouping measured data into data classes or histogram bins.
Discretization, quantization, or digitizing are very similar concepts. After binning, the fine-grain information of the original measured values is lost, and one uses only bin contents. The amount of information lost in this way is negligible if the bin widths are small compared with the experimental resolution.
Many statistical methods, notably those based on the chi-square distribution, require that data be binned, and that the bins satisfy certain constraints, namely that the number of events in each bin be not less than a certain minimum number so that the distribution of expected events per bin is approximately Gaussian. Opinions differ on the minimum number of events required, but this is usually taken as being between five and ten, provided only a few bins have this minimum number. There is no reason why bins should be of equal width, except for convenience of computation (e.g. in image processing), and many studies indicate that the statistically optimal binning is that which gives equally probable bins.
Where the amount of data is so small that wide bins are necessary, it is preferable to avoid binning by using other methods if possible. For example, use the maximum likelihood fit instead of the least squares fit, and use the Kolmogorov test or the Cramer-Smirnov-Von-Mises test rather than the one-dimensional chi-square test.


An algebraic expression that is the sum of two terms.

Binomial theorem

The theorem that tells how to expand the expression (a + b)n.
The theorem that gives the terms of the expansion of a binomial expression [eg. (p+q)] raised to a particular power n [eg. (p+q)^n]


Higher concentration of a chemical in cells than in the nonliving surroundings.


A method of determining the effect of a compound by quantifying its effect on living organisms or their component parts.The determination of the activity or concentration of a chemical by its effect on the growth of an organism under experimental conditions


Increasing the activity of bacteria that decompose pollutants.A technique used in bioremediation.

Bioavailable testosterone

The fraction of circulating testosterone that readily enters cells and better reflects the bioactivity of testosterone than does the simple measurement of serum total testosterone.


An enzyme, used to catalyze a chemical reaction.


A property of molecules or chemicals that refers to their usefulness as food because they can be metabolized (metabolism) by organism.


The microbially mediated process of chemical breakdown of a substance to smaller products caused by micro-organisms or their enzymes.


The collective richness and variety of all forms of life - bacteria, archaea, eukarya and associated viruses.


The term bioelectricity refers to the use of charged molecules and elements (= ions) in biological systems.The movement and placement of charges has a great influence on molecular interactions between molecules and thus affects structure and function of proteins, DNA, and cell membranes. The latter are able to stabilize local charge separation in form of ion gradients which are a form of energy storage but also serve as information processing device (see Action potential).

Bioelectric impedance analysis

A seemingly simple method for determining the lean body mass. Abbreviated BIA.
There are two methods of BIA. One involves standing on a special scale with footpads. A harmless amount of electrical current is sent through the body, and then the percentage of body fat is calculated. The other type of BIA involves electrodes usually placed on a wrist and an ankle and on the back of the right hand and on the top of the foot. The change in voltage between electrodes is measured. The person's body fat percentage is then calculated from the results of the BIA.


Adherent layer of bacteria and/or other microorganisms on a solid surface bound together in a bacterially-derived polysaccharide matrix that is protective for the organisms; generally occuring at a liquid/solid interface and often developing into a complex ecological community (e.g., dental plaque bound tother by dextrans)

Biogeochemical cycles

The various nutrient circuits, which involve both biotic and abiotic components of ecosystems.

Bioidentical hormones

Compounds that have exactly the same chemical and molecular structure as hormones that are produced in the human body.Though any hormone can be made to be "bioidentical," the term is often used to describe allegedly custom-compounded formulations containing estrogens, progesterone, and androgens. There is no evidence that they are any safer or more effective than FDA-approved hormone preparations.

BioInformatics (also known Systems biology)

A scientific discipline that comprises all aspects of the gathering, storing, handling, analysing, interpreting and spreading of biological information. The sum of the computational approaches to analyze, manages, and store biological data, using computerised databases and algorithms for analysis and statistical capabilities.
Bioinformatics involves the analysis of biological information using computers and statistical techniques, the science of developing and utilizing computer databases and algorithms to accelerate and enhance biological research. It comprises the development and application of computational algorithms for the purpose of analysis, interpretation, and prediction of data for the design of experiments in the biosciences.
Bioinformatics is used in analyzing genomes, proteomes (protein sequences), three-dimensional modeling of biomolecules and biologic systems, etc.  In genome projects this includes the development of methods to search databases quickly, to analyze DNA sequence information, and to predict protein sequence and structure from DNA sequence data. Training in informatics requires backgrounds in molecular biology and computer science, including database design and analytical approaches.


A method (biological ballistics) of transfecting cells by bombarding them with microprojectiles coated with DNA. A method developed to inject DNA into cells by mixing the DNA with small metal particles and then firing the particles into the host cell at very high sped.

Biological clock

Proposed internal factor(s) in organisms that governs functions that occur rhythmically in the absence of external stimuli.There are beleieved to be mutiplte such clocks, located in the brain in structures such the suprachisamatic nucleus, the pineal gland etc.  These neurons in these regions may have an inherent rhytmicity that generates a “clock” for timing of body events, e.g., the circadian clock.  Hormones (e.g., melatonin) may often be involved in exerting the effects of these neurons on widespread body structures to entrain them to the rhythm.

Biological control agent

Vaccines, therapeutic serums, toxoids, antitoxins and analagous biological products used to induce immunity to infectious siseases or harmful substances of biological origin.

Biological indicator system

A system that uses a biological organism (bacteria or enzyme) to determine whether a process cycle has met the specified requirements.
(See Chemical indicator system)

Biologically at risk

History of prenatal, perinatal, neonatal, or early developmental events that may damage the central nervous system (e.g., very low birth weight, intraventricular bleed).

Biological magnification

A trophic process in which retained substances become more concentrated with each link in the food chain.

Biological response modifier therapy

Treatment to boost or restore the ability of the immune system to fight cancer, infections, and other diseases. Also used to lessen certain side effects that may be caused by some cancer treatments. Agents used in biological response modifier therapy include monoclonal antibodies, growth factors, and vaccines. These agents may also have a direct anti-tumor effect.
Also called biological therapy, biotherapy, BRM therapy, and immunotherapy.

Biological species

Organisms are classified in the same species if they are potentially capable of interbreeding and producing fertile offspring.

Biological value (of proteins)

The biological value of a protein refers to the how much of the nitrogen content of food is retained by the body.The biological value of proteins ranges from 50 to 100 percent and is a measure of how much dietary protein source can support growth. Animal proteins have biological values of 70 percent or higher, and plant proteins have biological values of 50 to 70


Agents, such as vaccines, that give immunity to diseases or harmful biotic stresses.
Includes genetic resources, organisms or parts thereof, populations, or any other biotic component of ecosystems with direct, indirect or potential use or value for humanity.


A chemical reaction that causes an organism to glow.


Increasing concentrations of a chemical with higher trophic levels.


The total dry weight of all organisms in a particular sample, population, or area.


Major types of communities and ecosystems that are recognizable in large geographic areas.


The science of collecting and analyzing biologic or health data using statistical methods. Biometry may be used to help learn the possible causes of a cancer or how often a cancer occurs in a certain group of people.


A new field in agriculture using recombinant DNA technology to introduce genes into plants or livestock for the purpose of expressing a drug or nutrient in quantities not found in nature.Biopharming may be used to produce antibodies in cow milk or hormones in plant leaves or seeds for easy harvesting. The plant or animal serves as a natural bioreactor and has become a genetically modified organism in the process.


The removal of cells or tissues for examination by a pathologist, for examination under a microscope or for other tests on the cells or tissue.
There are many different types of biopsy procedures. The most common types include: (1) incisional biopsy, in which only a sample of tissue is removed; (2) excisional biopsy, in which an entire lump or suspicious area is removed; and (3) needle biopsy, in which a sample of tissue or fluid is removed with a needle. When a wide needle is used, the procedure is called a core biopsy. When a thin needle is used, the procedure is called a fine-needle aspiration biopsy. (Source: NIH National Cancer Institute)


The use of biological organisms such as plants or microbes to aid in removing hazardous substances from an area.


All of the plant and animal life of a particular region.


Application in biology to manipulate the structure and function of biological systems into forms not found in nature.Often used to improve or facilitate cellular processes such as energy metabolism, gene transfer between unrelated species, or the engineering of enzymes for the large scale synthesis of drugs.


Pertaining to life or living organisms.


A water-soluble B vitamin.Often used in combination with the protein streptavidin in biochemical assays or in histology to visualise cells stained with specific agents.


An organism which is dependent on a living host organism as a source of nutrients.

Bipolar disorder

1. A mood disorder with elevated mood, usually accompanied by a major depressive episode. 2. More specifically: A major affective disorder in which there are episodes of both mania and depression; formally called manic depressive psychosis, circular or mixed type.
Bipolar disorder may be subdivided into manic, depressed or mixed types on the basis of currently presenting symptoms.A mild form of bipolar disorder is sometimes labelled cyclothymic disorder.

Bipolar prosthesis

A two component prosthesis used for hemiarthroplasties in which one prosthetic component is fixed rigidly in place on one side of the joint and the second component with which the first articulates is inserted loosely on the other side of the joint. The prosthesis is named after the fixed component. Motion of the across the joint component puts less stress on bone and the articulating surfaces. As an example, one design of a femoral bipolar hemiarthroplasty consists of a prosthetic femoral head articulating with a polyethylene liner in the acetabular component. The liner is inside a metal shell and can move with respect to the shell. The shell is press fitted into the acetabulum either with or without reaming of the acetabulum. The shell can move within the acetabulum. It is important when reading x-rays of bipolar implants to be aware that the across the joint component is mobile and not to interpret a change in position of this component as necessarily indicative of loosening. See unipolar prosthesis.


Production process making use of living organisms, their parts (e.g., cells) or their products (e.g., enzymes).


A container used for bioprocessing.A contained vessel or other structure in which chemical reeactions are carried out (usually on an industrial scale), mediated by a biological system, enzymes or cells. A bioreactor can range in size from a small container to an entire building.


The use of biological agents to reclaim soils and waters polluted by substances hazardous to human health and/or the environment. It is an extension of biological treatment processes that have been used traditionally to treat wastes in which micro-organisms typically are used to biodegrade environmental pollutants.

Biosensor technology

The use of cells or biological molecules in an electronic system to detect specific substances. Consists of a biological sensing agent coupled with a microelectronic circuit.


Production of a chemical by a living organism.


All of the organisms, including animals, plants, fungi, and microorganisms, found in a given area.


Small area with uniform biological conditions (climate, soil, altitude, etc.).


Group of genetically identical individuals.


To cut something in half.


The smallest unit of information that a computer can work with.Each bit is either a one or a zero. Computers work with chunks of bits rather than one bit at a time; the smallest chunk of bits a computer usually works with is a byte which is 8 bits.


The highly saline liquor which remains after most of the salt has crystallised from brine.

Bivalent (in genetics)

During the prophase of meiosis I, homologous chromosomes pair and form synapses. The paired chromosomes are called bivalents. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.


Having a pair of longitudinal stripes.


Any pouch or other flexible enclosure that can hold liquids or gases but usually refers to the hollow organ in the lower abdomen that stores urine -- the urinary bladder. The kidneys filter waste from the blood and produce urine, which enters the bladder through two tubes called ureters. Urine leaves the bladder through another tube, the urethra . In women, the urethra is a short tube that opens just in front of the vagina . In men, it is longer, passing through the prostate gland and then the penis . Infection of the bladder is called cystitis .


A computer program that identifies homologous (similar) genes in different organisms, such as human, fruit fly, or nematode.


The fluid-filled cavity at the center of a blastula.


An early, pre-implantation stage of the developing embryo, consisting of of about 150 cells produced by cell division following fertilization.The developmental stage of the fertilized ovum by the time it is ready to implant; formed from the morula. It is a sphere made up of an outer layer of cells (the trophoblast), a fluid-filled cavity (the blastocoel), and a cluster of cells on the interior (the inner cell mass).


Stage when the oocyte membrane folds inward between the nuclei, eventually partitioning off each somatic nucleus into a single cell


Disklike area on the surface of a large, yolky egg that undergoes cleavage and gives rise to the embryo.


One of the cells formed by division of the fertilized egg making up the blastula.


The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes.The embryonic structure present during gastrulation and formed by invagination of the endoderm.


The hollow ball of cells marking the end stage of cleavage during early embryonic development.A ball of cells surrounding a fluid-filled cavity (the blastocoel) that is produced by the repeated cleavage of a zygote.

Bleaching (of food)

Treatment to reduce natural pigments (carotenoids, chlorophylls and xanthophylls) and other impurities such as cations of iron, copper and zinc.

Blind study

A study in which the experimenter is unaware of which test procedure the animal has received. Compare double-blind.


Areas in the primary visual cortex (V1) which are rich in the enzyme cytochrome oxidase.Blobs are found predominantly in cortical layers II and III and to a lesser extent layers V and VI.


On magnetic tape, a physical chunk of information separated from other blocks by an
interblock gap of blank space. The computer reads and processes the information from a tape in blocks. The size of a block is typically a multiple of the size of a physical record .Hence Blocksize = On magnetic tape, the size of a block. Note that when a smaller blocksize is used, a greater number of interblock gaps are necessary to record a given amount of information and thus a greater amount of tape is used.

Blocking (of speech)

Interruption of a train of speech before a thought or idea has been completed. After a period of silence, which may last from a few seconds to minutes, the person indicates that he or she cannot recall what he or she has been saying or meant to say. Blocking should be judged to be present only if the person spontaneously describes losing his or her thought or if upon questioning by the interviewer, the person gives that as a reason for pausing.

Blood Brain Barrier

A selectively permeable barrier formed by a network of blood vessels with closely spaced cells that makes it difficult for potentially toxic substances (such as anticancer drugs) to penetrate the blood vessel walls and enter the brain.The capillaries are packed more tightly than throughout the body so that the BBB consists of very high resistance tight junctions between the cerebral capillary endothelial cells, which are maintained in this state by astrocytes. These closely packed capillaries supply blood to the brain and spinal cord. The BBB serves to prevent the passage of large molecules and cells into the CNS. Large molecules cannot permeate through the narrow spaces, however fat soluble (lipophilic) molecules can dissolve through the capillary cell membranes and are absorbed into the brain. The endothelial cells of the capillaries of the brain and spinal cord are linked by tight junctions which prevent direct contact between plasma and cells of the central nervous system. Lipophilic drugs can diffuse across this barrier; some nutrients are actively transported across it. Other substances may have very poor access to the brain.

Blood Group Antigens

Glycoproteins and glycolipids (proteins and phospholipids attached to carbohydrates) on cell membranes of Red Blood Cells, acting as antigens (substances causing the generation of antibodies and can cause an immune response) that determine blood types.
There are three types of blood-group antigens, O, A, and B, differing only slightly in the composition of carbohydrates.All humans contain enzymes which catalyze the synthesis of the O antigen.  Humans with A-type blood also contain an additional enzyme which adds N-Acetylgalactosamine to the O antigen.  Humans with B-type blood contain another enzyme which adds Galactose to the O antigen.  Humans with AB-type blood contain both A-type and B-type enzymes while humans with O-type blood lack both types of enzymes.
(Source: http://www.web-books.com/MoBio/Free/Ch1B5.htm)

Blood pressure

The hydrostatic pressure created by the heart that forces blood to move through the arteries.The blood pressure can be differentiated into the systolic and diastolic blood pressures. Systolic blood pressure, the pressure measured during contraction of the ventricles, averages about 120 mm Hg in arteries of the systemic circulation (for healthy, young adults). The diastolic blood pressure, measured during ventricle relaxation, is about 80 mm Hg in these arteries. As blood travels through the arterial system, resistance from the walls of the blood vessels reduces the pressure and velocity of the blood. Blood pressure drops sharply in the arterioles and falls to between 40 and 20 mm Hg in the capillaries. Blood pressure descends further in the venules and approaches zero in the veins.


A technique for transferring a specific protein or nucleic acid from an electrophoresis gel matrix to a microporous membrane, for detecting one RNA within a mixture of RNAs (a Northern blot) or one type of DNA within a mixture of DNAs (a Southern blot)..A blot can prove whether that one species of RNA or DNA is present, how much is there, and its approximate size. Basically, blotting involves gel electrophoresis, transfer to a blotting membrane (typically nitrocellulose or activated nylon), and incubating with a radioactive probe. Exposing the membrane to X-ray film produces darkening at a spot correlating with the position of the DNA or RNA of interest. The darker the spot, the more nucleic acid was present there.
The DNA is first transferred from the gel to a membrane by capillary action. Fluid wicks from the gel through the blotting membrane to several layers of absorbent paper, but the nucleic acids stick to the membrane. Baking the filter fixes the DNA or RNA to the filter.

Then specific bands are detected by hybridization. The filter membrane is incubated with radioactive probe, which hybridizes to some bands. After the filter is washed (to remove unused probe), an X-ray film exposed to the filter will show which bands have hybridized.

Blunt-end ligation

The ligating or attaching of blunt-ended pieces of DNA by T4 DNA ligase.
Used in creating hybrid vectors.

Blurred vision

Lack of sharpness of vision with, as a result, the inability to see fine detail. Blurred vision can occur when a person who wears corrective lens is without them. Blurred vision can also be an important clue to eye disease.

B lymphocyte

A type of white blood cell that produces antibodies.


The baseline standard expected to yield the highest possible bound response is termed the Bmax.In competitive binding assays, the Bmax is the Bzero baseline standard. In sandwich assays, the Bmax is the maximum binding baseline standard. If a Bmax baseline standard is not assayed, the raw responses can be normalized to any standard. In one standard assays, the Bmax is the index standard. The maximum amount of drug (usually expressed in picomoles per mg protein) which can bind specifically to the receptors in a membrane preparation. If one drug molecule binds to each receptor, it also indicates the concentration of receptors in the tissue.


The baseline standard expected to yield the lowest possible bound response is termed the Bmin.In competitive binding assays, the Bmin is the NSB, a zero standard with no binder added. In sandwich assays, the Bmin is the zero blank baseline standard. If a Bmin baseline standard is not assayed, the raw responses can be normalized to any standard. In one standard assays, the Bmin is the reagent blank.

B memory cells

Long-lived B cells that are produced after an initial exposure to an antigen and play an important role in secondary immunity. B memory cells remain in the body and facilitate a more rapid response if the antigen is encountered again.


A method for determining the lean body mass. The BOD POD is a computerized, egg-shaped chamber. Using the same whole-body measurement principle as underwater weighing, the BOD POD measures a subject's mass and volume, from which their whole-body density is determined. Using these data, body fat and lean muscle mass can then be calculated.

Body hearing aid

A hearing aid with a microphone, amplifier and battery worn on the chest and with a cord-connected receiver worn at the ear.

Boiling point

The temperature at which a liquid turns to a vapour.

Boiling point elevation

One of the colligative properties. The boiling point of a solution is increased over that of water by the presence of solutes.The extent of the increase is a function of both concentration and molecular weight of the added solutes.


1) A single dose of drug usually injected into a blood vessel over a short period of time.
2) A mass of chewed food mixed with salivary secretions that is propelled into the oesophagus during the swallowing phase of digestion.


A chemical link between atoms.

Bond energy

The energy required to form a particular chemical bond.The quantity of energy that must be absorbed to break a particular kind of chemical bond; equal to the quantity of energy the bond releases when it forms.

Bond strength

The strength with which a chemical bond holds two atoms together; conventionally measured in terms of the amount of energy, in kilocalories per mole, required to break the bond.

Bone age X-ray

An x-ray of the left hand and wrist. This x-ray may be a part of the growth evaluation. The doctor will compare the child’s chronological age (actual age) with their skeleton age (bone maturity). Delays or advancements in skeletal age from the child’s actual age may help support an endocrine diagnosis.

Bone-conduction hearing aid

A hearing aid that uses a bone vibrator pressed against the skull to transmit amplified sound directly to the inner ear.

Bone density or Bone mass or Bone mineral density

A measure of the amount of minerals (mostly calcium and phosphorous) contained in a certain volume of bone. A bone mineral density (BMD) test measures the density of minerals (such as calcium) in bones using a special X-ray, computed tomography (CT) scan, or ultrasound. Bone density (mass) measurements are used to diagnose osteoporosis, to see how well osteoporosis treatments are working, and to predict how likely the bones are to break. Low bone density can occur in patients treated for cancer.

Bone morphogenetic proteins

Bone morphogenetic proteins, BMPs, are a group of endogenous proteins that stimulate bone growth. Recombinant human bone morphogenetic protein two, rhBMP-2, is the only FDA approved BMP for human use. It is used with bone grafts and spinal cages for interbody fusion of vertebral bodies.

Bone marrow stromal cells

A population of cells found in bone marrow that are different from blood cells, a subset of which are multipotent stem cells, able to give rise to bone, cartilage, marrow fat cells, and able to support formation of blood cells.


Describes any operation which allows a system to generate itself from its own small well-defined subsets (e.g. compilers, software to read tapes written in computer-independent form). The word is borrowed from the saying pull yourself up by your own bootstraps .In statistics, the bootstrap is a method allowing one to judge the uncertainty of estimators obtained from small samples, without prior assumptions about the underlying probability distributions. The method consists of forming many new samples of the same size as the observed sample, by drawing a random selection of the original observations, i.e. usually introducing some of the observations several times. The estimator under study (e.g. a mean, a correlation coefficient) is then formed for every one of the samples thus generated, and will show a probability distribution of its own. From this distribution, confidence limits can be given.

Borderline personality disorder

Instability in a variety of areas, including: Interpersonal relationships, behavior, mood and self-image. Interpersonal relationships are often intense and unstable, with marked shifts of attitude. Frequently there is impulsive and unpredictable behavior which is potentially physically self-damaging. Mood is often unstable with marked shifts from normal to dysphoric or with inappropriate intense anger or lack of control of anger. A profound identity disturbance may be manifested by uncertainty about self-image, gender identity, long-term goals or values. There may be chronic feelings of emptiness or boredom or brief episodes of psychosis.

Borg scale

A subjective scale to measure exercise intensity, used in the measure known as Rate of Perceived Exertion or RPE.The most common RPE scale. On the Borg scale there are numbers from 6 through 20. Each number corresponds to a certain level of intensity. Levels 6 to 11 are considered light intensity, moderate intensity would be 12 to 14, and vigorous would be 15 to 17. Maximum intensity would be 18 to 20. RPE takes into account how hard the entire body is working. It's not just about your legs getting tired or your feet being sore.  It takes in account breathing rate, heart rate, muscle fatigue and perspiration. (See RPE)

Bottle (or flask) cells

Epithelial cells found at the initial site of gastrulation, lining the initial archenteron, which temporarily become bottle-shaped. They maintain contact with the outer surface of the embryo, but the majority of the cell is inside the embryo.


Acute food poisoning caused by eating toxin produced by growth Clostridium Botulinum bacteria in moist, lowacid food, containing less than 2% oxygen and stored between 40 degrees and 120 degrees Fahrenheit. Proper heat processing destroys this bacterium in canned food. Freezer temperatures inhibit its growth in frozen food. Low moisture controls its growth in dried food. High oxygen controls its growth in fresh foods.

Bound fraction

The bound fraction of an immunoassay reaction is portion containing all of the ligand-binder complexes.

Bovine spongiform encephalopathy (BSE) (also known as "mad cow disease”)

It is a rare, chronic degenerative disease affecting the brain and central nervous system of cattle, classified as a transmissible spongiform encephalopathy (TSE).
The causative agent for BSE has not been determined and has been variously attributed to a "slow virus" or a "virino", or a "prion" (an aberrant form of a normal prion protein) that causes the normal protein to conform to its aberrant shape, which leads to a cascade of abnormal proteins accumulating in brain cells. The accumulation of protein plaques causes cell death and leaves holes in the brain giving a "sponge-like" appearance. The etiologic agent is extremely resistant to destruction.
Cattle with BSE lose their coordination, develop abnormal posture and experience changes in behavior. The incubation period for BSE in cattle is 2-8 years and clinical symptoms take 4-5 years to develop, followed by death in a period of several weeks to months unless the affected animal is destroyed sooner.


Another name for the intestine . The small bowel and the large bowel are the small intestine and large intestine , respectively.

Bowman’s capsule (also known as Glomerular capsul)

A cup-shaped structure with a thin double membrane surrounding the glomerulus of each nephron of the vertebrate kidney. It is the initial expanded segment of the nephron that serves as a filter to remove organic wastes, excess inorganic salts, and water.


A small portion of a gene or protein that appears in many genes or proteins that are related in structure.The box usually has some specific function, sometimes called a "motif", like binding DNA or interacting with specific proteins or other molecules.

BPI (Bytes per inch)

A measure of the storage density used on magnetic tape.A 2400 foot tape at 6250 BPI could theoretically store about 180 megabytes (million bytes) of data. In practice, however, one seldom find tapes with more than about 100-150 megabytes of data. See also blocksize.


A type of radiation therapy in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called implant radiation therapy, internal radiation therapy, and radiation brachytherapy.


A slowing of the heart rate.


Slowness of movement.

Brain injury

Acquired Brain Injury: The implication of this term is that the individual experienced normal growth and development from conception through birth, until sustaining an insult to the brain at some later time which resulted in impairment of brain function.
Closed Brain Injury: Occurs when the head accelerates and then rapidly decelerates or collides with another object (for example the windshield of a car) and brain tissue is damaged, not by the presence of a foreign object within the brain, but by violent smashing, stretching, and twisting, of brain tissue.
Mild Brain Injury: A patient with a mild traumatic brain injury is a person who has had a traumatically-induced physiological disruption of brain function, as manifested by at least one of the following: 1) any period of loss of consciousness, 2) any loss of memory for events immediately before or after the accident, 3) any alteration in mental state at the time of the accident (e.g., feeling dazed, disoriented, or confused), 4) focal neurological deficit(s) which may or may not be transient; but where the severity of the injury does not exceed the following: a) loss of consciousness of approximately 30 minutes or less; b) after 30 minutes, an initial Glasgow Coma Scale score of 13-15; c) Post Traumatic Amnesia not greater than 24 hours.
Traumatic Brain Injury: Damage to living brain tissue caused by an external, mechanical force. It is usually characterized by a period of altered consciousness (amnesia or coma) that can be very brief (minutes) or very long (months/indefinitely). The specific disabling condition(s) may be orthopedic, visual, aural, neurologic, perceptive/cognitive, or mental/emotional in nature. The term does not include brain injuries that are caused by insufficient blood supply, toxic substances, malignancy, disease-producing organisms, congential disorders, birth trauma or degenerative processes.
Closed brain injuries typically cause diffuse tissue damage that results in disabilities which are generalized and highly variable.

Brain Plasticity

The ability of intact brain cells to take over functions of damaged cells or to change their responses as a function of the organism’s experiences with the world.

Brain Scan

An imaging technique in which a radioactive dye (radionucleide) is injected into the blood stream and then pictures of the brain are taken to detect tumors, hemorrhages, blood clots, abscesses or abnormal anatomy.


The lower extension of the brain where it connects to the spinal cord: the hindbrain and midbrain of the vertebrate central nervous system. In humans, it forms a cap on the anterior end of the spinal cord, extending to about the middle of the brain.Neurological functions located in the brain stem include those necessary for survival (breathing, heart rate) and for arousal (being awake and alert).


Graphical representation of an evolutionary lineage in a phylogenetic tree diagram.

Branched DNA (bDNA) assay

A signal amplification technology that detects the presence of specific nucleic acids by measuring the signal generated by many branched, labeled DNA probes.

Branchial arches (also known as visceral arches, gill arches, or pharyngeal arches)

Columns of mesenchyme found in the neck of the developing vertebrate embryo derived from cranial neural crest. In lower vertebrates, blood vessels formed here become part of the gills; in higher vertebrates derivatives include portions of the jaw and middle ear.

Branch migration

1. The process in which a crossover point between two DNA duplexes slides along theduplexes.
2. The process by which a single invading DNA strand extends its partial pairing with its complementary strand as it displaces the resident strand from a DNA duplex.

Brazelton scale

The Neonatal Behavioral Assessment Scale. Useful for scoring interactive behavior. May be useful as predictive of subsequent functional ability.

Breakage and reunion (in genetics)

The general mode by which recombination of DNA occurs. DNA duplexes are broken and reunited in a crosswise fashion according to current models.

Breakpoint (in genetics)

Refers to sites of breakage when chromosomes break (and recombine).

Breakthrough pain

Intense increases in pain that occur with rapid onset even when pain-control medication is being used. Breakthrough pain can occur spontaneously or in relation to a specific activity.

Breast duct endoscopy

A method used to examine the lining of the breast ducts to look for abnormal tissue.
A very thin, flexible, lighted tube attached to a camera is inserted through the nipple, and threaded into the breast ducts deep in the breast. Tissue and fluid samples may be removed during the procedure.

Bregma and Lambda

Landmarks on the surface of the skull made by the intersection of particular cranial bones.
Bregma = the junction of the coronal and sagittal sinuses.
Lambda = the junction of the sagittal and lamboid sutures.


One of the three possible ways to generate X-rays, and the one commonly used to create X-rays for food irradiation. Literally translated from the German it means "braking" (brems) "radiation" (strahlung). Bremsstrahlung.

Brent’s method

A particularly simple and robust method to find a minimum of a function f(x) dependent on a single variable x.The minimum must initially be bracketed between two values x=a and x=b. The method uses parabolic interpolation as long as the process is convergent and does not leave the boundaries (a,b), and interval subdividing methods otherwise. The algorithm requires keeping track of six function points at all times, which are iteratively updated, reducing the minimum-enclosing interval continually.

Bridging cross

A cross made to transfer alleles between two sexually isolated species by first transferring the alleles to an intermediate species that is sexually compatible with both.

Brix hydrometer scale
(Also known as the Plato scale)

Sugar content of a solution at a given temperature; measure of the density of a solution, expressed in degrees Brix. Named for AFW Brix, a nineteenth-century German inventor.
The Brix (sugar content) is determined by a hydrometer, which indicates a liquid's specific gravity (the density of a liquid in relation to that of pure water). Each degree Brix is equavalent to 1 gram of sugar per 100 grams of liquid.
The °Brix of a solution = the % Sucrose of the solution at room temperature.
Numerically equivalent to the Balling hydrometer scale, but is chiefly used by sugar refineries and vintners, whereas the Balling scale is used by brewers.


A lung disorder in which the bronchial tubes become enlarged and distended forming pockets where infection may develop. The bronchial walls may also be damaged which reduces the lung’s ability to expel foreign material.
There are several known causes including:

  • Underlying genetic disease such as cystic fibrosis - where the mucus in the bronchial tubes is too thick - or 'primary ciliary dyskinesia' - where the hairs lining the bronchial tubes do not work properly
  • Blockage caused by scarring. When damaged bronchial tubes heal, they can be scarred. The scarring can lead to blockages. This can happen if you've had infections such as childhood pneumonia, whooping cough or measles
  • Blockage of the bronchial tubes by food, like peanuts
  • Lack of immunity to infection, for example: a lack of antibodies which occasionally happens if you get a virus infection in adult life
  • Heartburn - but this is rare.

However, over half the people with bronchiectasis have no obvious cause for it.


Inflammation and blockage of the tiniest airways in a baby's lungs, usually caused by a virus. The most common virus to cause bronchiolitis is Respiratory Syncytial Virus, known as 'RSV’.Bronchiolitis makes the baby cough and become breathless.Usually bronchiolitis starts like a simple cold. The most common feature is a rasping cough. Many babies will only have mild symptoms and can be cared for at home. However some babies experience more severe symptoms and have difficulty in feeding and become very breathless. They may have low levels of oxygen in the blood. Most babies get better without treatment but some will need to be admitted to hospital. This can happen if they are having difficulty in feeding and coughing a lot, or they might need oxygen for a short period.

Bronchiolitis obliterans organising pneumonia (BOOP)

A swelling of the small airways in the lung, causing blockages in the outermost parts of the lung.
BOOP gets its name from the fact that it closely mimics pneumonia infections. It affects men and women equally, usually beginning in their 40s or 50s, but has been reported in children with underlying cancer.
BOOP has many causes, including:

  • infection
  • toxic and fume exposure (most commonly nitrogen dioxide)
  • collagen vascular disease (rheumatoid arthritis, SLE)
  • bone marrow and heart-lung or lung transplantation
  • drug reaction (penicillin)

However the majority of BOOP cases are of idiopathic (unknown) origin.


Constriction of the smooth muscle in airways in the lungs due to exposure to irritant chemicals or to an immunological reaction involving release of inflammatory mediators.


A type of drug that causes small airways in the lungs to open up. Bronchodilators are inhaled and are used to treat breathing disorders, such as asthma or emphysema.

Bronchopulmonary dysplasia (BPD).

A chronic lung disease of babies, which develops most commonly in the first 4 weeks after birthUnlike an adult with a lung disease, a baby can grow healthy new lung tissue. Babies with BPD often have continuing respiratory problems. Despite these problems, most outgrow their respiratory symptoms by school age and are able to participate then in normal physical activity. BPD occurs when the lungs and airways of an infant are damaged as a result of being on a respirator.


A technique or procedure that involves visually examining the tracheobronchial tree.
The examination is done using an endoscope or bronchoscope (flexible fiber optic or rigid) inserted through the mouth and trachea for direct viewing of structures or for projection on a monitor, for diagnostic or therapeutic indications.


Involuntary sudden movement or convulsive contraction of the muscular coats of the bronchus

Bronchus (pl. bronchi)

One of a pair of respiratory tubes branching into either lung at the lower end of the trachea; it subdivides into progressively finer passageways, the bronchioles, culminating in the alveoli.

Bronsted-Lowry acid / base

See Arrhenius acid

Brown Sequard syndrome.

Ipsilateral paralysis and loss of discriminatory and joint sensation and contralateral loss of pain and temperature sensation due to damage to one half of the spinal cord.

Brush border

The collection of microvilli forming a border on the intestinal side of the epithelial cells of the small intestine.


Repetitive grinding of the teeth.


Relating to structures associated with the mouth.


A system capable of resisting changes in pH even when acid or base is added, consisting of a conjugate acid-base pair in which the ratio of proton acceptor to proton donor is near unity.Hence Buffer system = Pairs of weak acids and bases that maintain body fluid pH.A substance that consists of acid and base forms in solution and that minimizes changes in pH when extraneous acids or bases are added to the solution.

Bulbar region

An area of the brain composed of the cerebellum, medulla and pons.
Basically, the bulbar region is made up of the brain stem minus the midbrain and plus the cerebellum. The bulbar region is responsible for many involuntary functions that keep us alive.

Bulbourethral glands

Small glands near the male urethra that secrete mucus.One of a pair of glands near the base of the penis in the human male that secrete fluid that lubricates and neutralizes acids in the urethra during sexual arousal.

Bulbus Olfactorius

Nerve cells of the brain in which the aroma stimuli transmitted through the receptor cells are further processed.

Bulimia nervosa

An eating disorder in which there are frequent episodes of uncontrolled binge eating followed by self-induced vomiting or other extreme measures to prevent weight gain.

Bulk flow

The movement of water due to a difference in pressure between two locations.

Bundle of His

In the vertebrate heart, a group of muscle fibers that carry impulses from the atrioventricular node to the walls of the ventricles; the only electrical bridge between the atria and the ventricles.


The ability to float.The upward forces exerted by a fluid on a body in it

Buoyant density

A measure of the tendency of a substance to float in some other substance. 
Large molecules are distinguished by their differing buoyant densities in some standard fluid. Measured by density-gradient ultracentrifugation.
e.g., Buouyant density of DNA = A measure of the density of DNA determined by the equilibrium point reached by DNA after density gradient centrifugation.

Burkitt lymphoma

A cancer of the lymphatic system manifested by tumours in the jaw. Often associated with a translocation bringing a specific onco gene next to a novel regulatory element.

Bursae (singular = Bursa)

Small, flat sacs lined with synovial membrane and filled with synovial fluid, found between a bone and a tendon or muscle.Bursae act as cushions to reduce friction between tendons and bones, by helping the tendon or muscle slide smoothly over the bone.


Inflammation (swelling, pain, and warmth) of a bursa.Bursitis may be caused by long-term overuse, trauma, rheumatoid arthritis, gout, or infection. It usually affects the shoulder, knee, elbow, hip, or foot.


Eight bits. A byte is simply a chunk of 8 ones and zeros.
For example: 01000001 is a byte. A computer often works with chunks of bits rather than individual bits and the smallest chunk of bits that a computer usually works with is a byte. A byte is equal to one column in a file written in character format . Most data files distributed by ICPSR are in character format.