Medical Dictionary banner
Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


transduction (trans-duk′shun)
1. Transfer of genetic material (and its phenotypic expression) from one cell to another by viral infection. 2. A form of genetic recombination in bacteria. 3. Conversion of energy from one form to another. [trans- + L. duco, pp. ductus, to lead across] abortive t. t. in which the genetic fragment from the donor bacterium is not integrated in the genome of the recipient bacterium, and, when the latter divides, is transmitted to only one of the daughter cells. complete t. t. in which the transferred genetic fragment is fully integrated in the genome of the recipient bacterium. Davis battery model of t. a concept in which the positive endocochlear potential and the negative intracellular potential of the hair cells provide the electromotive force to pass current through the reticular lamina of the organ of Corti. general t. t. in which the transducing bacteriophage is able to transfer any gene of the donor bacterium. high-frequency t. specialized t. in which the donor bacterium contains not only the transducing, defective probacteriophage but also nondefective prophage that serves as “helper” virus, enabling most of the defective prophage particles to develop sufficiently to function as transducing agents. low-frequency t. specialized t. in which only a small portion of the prophage particles, because of their defectiveness, are able to develop sufficiently to serve as effective transducing agents. mechanoelectric t. the conversion of mechanical energy to electric energy by sensory cells such as auditory and vestibular hair cells. specialized t. t. in which the bacteriophage strain is able to transfer only some, or only one, of the donor bacterium genes. SYN: specific t.. specific t. SYN: specialized t..

transection (tran-sek′shun)
1. A cross-section. 2. Cutting across. SYN: transsection. [trans- + L. seco, pp. sectus, to cut]

transethmoidal (trans′eth-moy′dal)
Across or through the ethmoid bone.

transfection (trans-fek′shun)
A method of gene transfer utilizing infection of a cell with nucleic acid (as from a retrovirus) resulting in subsequent viral replication in the transfected cell. [trans- + infection]

1. Process of removal or transferral. 2. A condition in which learning in one situation influences learning in another situation; a carry-over of learning that may be positive in effect, as when learning one behavior facilitates the learning of something else, or may be negative, as when one habit interferes with the acquisition of a later one. SYN: transmission (1) . [L. trans-fero, to bear across] embryo t. after in vitro artificial insemination, the fertilized ovum is transferred at the blastocyst stage to the recipient's uterus or oviduct. Fourier t. SYN: Fourier analysis. gamete intrafallopian t. (GIFT) placement of the oocyte and sperm into the ampulla of the fallopian tube; a form of assisted reproduction. group t. the t. of a functional moiety from one molecule to another. Jones t. surgical procedure to treat claw deformities of the great toe in which the extensor hallucis longus tendon is transferred to the neck of the metatarsal; can also be used to correct claw deformities of the lesser toes. linear energy t. (LET) the amount of energy deposited by radiation per unit length of travel, expressed in keV per micron; protons, neutrons, and α particles have much higher LET than gamma or x-rays. A property of radiation considered in radiation protection. See relative biologic effectiveness.

transferases (trans′fer-as-ez)
Enzymes (EC class 2) transferring: one-carbon groups (2.1, including methyltransferases, 2.1.1; formyltransferases, 2.1.2; carboxyl- and carbamoyltransferases, 2.1.3; and amidinotransferases, 2.1.4); acyl residues (acyltransferases, 2.3); glycosyl residues (glycosyltransferases, 2.4, including hexosyltransferases, 2.4.1, and pentosyltransferases, 2.4.2); alkyl or aryl groups (2.5); nitrogenous groups (2.6); phosphorus-containing groups (2.7, phosphotransferases); and sulfur-containing groups (2.8, including sulfurtransferases, 2.8.1; sulfotransferases, 2.8.2; and CoA-t., 2.8.3). SYN: transferring enzymes. terminal t. enzymes that covalently add nucleotides to the 3′ end of polynucleic acids; E.G., DNA nucleotidylexotransferase. terminal deoxynucleotidyl transferase (TdT) a specialized DNA polymerase expressed in immature, pre-B, pre-T lymphoid cells, and acute lymphoblastic leukemia/lymphoma cells.

transference (trans-fer′ens)
1. Conveyance of an object from one place to another. 2. Shifting of symptoms from one side of the body to the other, as seen in certain cases of conversion hysteria. 3. Displacement of affect from one person or one idea to another; in psychoanalysis, generally applied to the projection of feelings, thoughts, and wishes onto the analyst, who has come to represent some person from the patient's past. counter t. See countertransference. extrasensory thought t. SYN: telepathy. t. love love expressed by the patient for the psychoanalyst as a manifestation of t. (3). negative t. t. characterized by predominantly hostile feelings on the part of the patient toward the analyst. passive t. the passage of an immunity or allergic susceptibility by the injection of serum of an animal or individual who has acquired an active immunity to the disease. positive t. t. characterized by predominantly friendly, respectful, and positive feelings on the part of the patient toward the analyst.

transferrin (trans-fer′in)
1. A nonheme β1-globulin of the plasma, capable of associating reversibly with up to 1.25 μg of iron per gram, and acting therefore as an iron-transporting protein. 2. A glycoprotein, found in mammalian milk (lactoferrin) and egg white (conalbumin, ovotransferrin), that binds and transports iron (Fe3+). [trans- + L. ferrum, iron, + -ia]

See entries under ribonucleic acid.

transfix (trans′fiks)
To pierce with a sharp instrument. [L. trans-figo, pp. -fixus, to pierce through, fr. figo, to fasten]

transfixion (trans-fik′shun)
A maneuver in amputation in which the knife is passed from side to side through the soft parts, close to the bone, and the muscles are then divided from within outward. [L. transfixio (see transfix)]


transformant (trans-for′mant)
A bacterium that has received genetic material (and its phenotypic expression) from another bacterium by means of transformation.

transformation (trans-for-ma′shun)
1. SYN: metamorphosis. 2. A change of one tissue into another, as cartilage into bone. 3. In metals, a change in phase and physical properties in the solid state caused by heat treatment. 4. In microbial genetics, transfer of genetic information between bacteria by means of “naked” intracellular DNA fragments derived from bacterial donor cells and incorporated into a competent recipient cell. [L. trans-formo, pp. -atus, to transform] cavernous t. of portal vein replacement of the portal vein by a number of collateral channels, a consequence of thrombosis. cell t. morphologic and physiologic changes including loss of contact inhibition resulting from infection of an animal cell by an oncogenic virus. Haldane t. the multiplication of inspired oxygen concentration by the ratio of expired to inspired nitrogen concentrations in the calculation of oxygen consumption or respiratory quotient by the open circuit method. Lobry de Bruyn-van Ekenstein t. the conversion of glucose to fructose and mannose in dilute alkali by enolization adjacent to the carbonyl group to form an enediol, a reaction analogous to certain biochemical transformations. logit t. a method of linearizing dose-response curves for radioimmunoassay techniques; i.e., logit B (bound)/Bo (initial binding) = log (B/Bo/1 − B/Bo). lymphocyte t. the t. into large, blastlike forms (immunoblasts) that occurs when lymphocytes are exposed to histoincompatible antigens (mixed lymphocyte culture) or mitogens. SEE ALSO: mixed lymphocyte culture test. nodular t. of the liver a rare condition in which nodules of hyperplastic hepatocytes develop without fibrosis or general loss of lobular architecture. SYN: nodular regenerative hyperplasia.

transfuse (trans-fuz′)
To perform transfusion.

transfusion (trans-fu′zhun)
Transfer of blood or blood component from one individual (donor) to another individual (receptor). [L. transfundo, pp. -fusus, to pour from one vessel to another] drip t. t. slow enough to measure by drops. exchange t. removal of most of a patient's blood followed by introduction of an equal amount from donors. SYN: exsanguination t., substitution t., total t.. exsanguination t. SYN: exchange t.. fetomaternal t. passage of fetal blood into maternal circulation. indirect t. t. into a patient of blood previously obtained from a donor and stored under suitable conditions. SYN: mediate t.. intramedullary t. t., most commonly in infants, into the medullary cavity of a long bone, usually the femur or tibia. intrauterine t. to treat erythroblastosis fetalis, Rh-negative blood is placed into the peritoneal cavity of the fetus. mediate t. SYN: indirect t.. placental t. return to the newborn via the umbilical vessels of some of the fetal placental blood. reciprocal t. an attempt to confer immunity by transfusing blood taken from a donor into a receiver suffering from the same affection, the balance being maintained by transfusing an equal amount from the receiver to the donor. subcutaneous t. an infusion of absorbable solutions beneath the skin. substitution t. SYN: exchange t.. total t. SYN: exchange t.. twin-twin t. direct vascular anastomosis, arterial or venous, between the placental circulations of twins.

transgene (trans′gen)
A newly introduced gene.

transgenesis (tranz-jen′e-sis)
Reproduction involving introduction of foreign species DNA into an ovum.

transgenic (trans-jen′ik)
Referring to an organism in which new DNA has been introduced into the germ cells by injection into the nucleus of the ovum.

transglottic (trans-glot′ik)
Vertical crossing of the glottis, as in the spread of carcinoma from the supraglottic to the infraglottic area.

transglucosylase (trans-gloo′ko-si-las)
SYN: glucosyltransferase.

transglutaminase (trans-gloo-ta′min-as)
A group of enzymes that catalyze the calcium-dependent acyl transfer reaction in which the amide moiety of peptide-bound glutaminyl residues serve as acyl donor; a specific t. covalently cross-links fibrin molecules between glutamine and the ε-amino group of a lysyl residue, thus producing a more stable fibrin clot; another t. participates in the formation of the chemically resistant envelope of the stratum corneum during terminal differentiation of keratinocytes.

transglycosidation (trans-gli-ko-sid′a-shun)
The transfer of a glycosidically bound sugar to another molecule.

transglycosylase (trans-gli′ko-si-las)
SYN: glycosyltransferase.

transhiatal (trans-hi-a′tal)
By way of a hiatus; e.g., t. esophagectomy, performed partially through the esophageal hiatus.

transient (trans′shent, -se-ent)
1. Short-lived; passing; not permanent; said of a disease or an attack. 2. A short-lived cardiac sound having little duration (less than 0.12 s) as distinct from a murmur; e.g., first, second, third, and fourth heart sounds, clicks, and opening snaps. [L. transeo, pres. p. transiens, to cross over]

transiliac (tran-sil′e-ak)
Extending from one ilium or iliac crest or spine to the other.

transilient (tran-sil′yent, -zil-)
Jumping across; passing over; pertaining to those cortical association fibers in the brain that pass from one convolution to another nonadjacent one. [L. transilio, to leap across, fr. salio, to leap]

transillumination (trans-i-loo′mi-na′shun)
Method of examination by the passage of light through tissues or a body cavity. [trans- + L. illumino, pp. -atus, to light up]

transinsular (tranz-in′soo-lar)
Across the insula or island of Reil.

transischiac (trans-is′ke-ak)
Extending from one ischium to the other.

transisthmian (trans-is′me-an)
Across any isthmus; specifically, across the isthmus of the fornicate gyrus, denoting the gyrus transitivus.

transition (tran-sish′un, -zish′un)
1. Passage from one condition or one part to another. 2. In polynucleic acid, replacement of a purine base by another purine base or a pyrimidine base by a different pyrimidine. [L. transitio, fr. transeo, pp. -itus, to go across] cervicothoracic t. the junction between the last cervical vertebra and first thoracic vertebra. isomeric t. the t. of a nuclear isomer to a lower quantum state; e.g., 131mXe → 131Xe + γ.

transitional (tran-sish′un-al, -zish-)
Relating to or marked by a transition; transitory.

transketolase (trans-ke′to-las)
A transferase bringing about the reversible interconversion of sedoheptulose 7-phosphate and d-glyceraldehyde 3-phosphate to produce d-ribose 5-phosphate and d-xylulose 5-phosphate, and also other similar reactions, such as hydroxypyruvate and an aldehyde into CO2 and an extended hydroxypyruvate; a part of the nonoxidative phase of the pentose phosphate pathway. SEE ALSO: transaldolase. SYN: glycolaldehydetransferase.

transketolation (trans′ke-to-la′shun)
A reaction involving the transfer of a ketole group (HOCH2CO–) from one compound to another.

translation (trans-la′shun)
1. A change or conversion into another form. 2. The rather complex process by which messenger RNA, transfer RNA, and ribosomes effect the production of protein from amino acids, the specificity of synthesis being controlled by the base sequences of the messenger RNA. 3. In dentistry, the movement of a tooth through alveolar bone without change in axial inclination. [L. translatio, a transferring, fr. transfero pp. -latus, to carry across] nick t. a technique in which a bacterial DNA polymerase is used to degrade a single strand of DNA that has been nicked and then to resynthesize that strand, often with labeled nucleoside triphosphates.

translocation (trans-lo-ka′shun)
1. Transposition of two segments between nonhomologous chromosomes as a result of abnormal breakage and refusion of reciprocal segments. 2. Transport of a metabolite across a biomembrane. [trans- + L. location, placement, fr. loco, to place] bacterial t. the movement of bacteria or bacterial products across the intestinal membrane to emerge either in the lymphatics or the visceral circulation. balanced t. t. of the long arm of an acrocentric chromosome to another chromosome; an individual with a balanced t. has a normal diploid genome and is clinically normal but has a chromosome count of 45 and as a result of asymmetric meiosis may have children lacking the genes on the translocated segment or have them in trisomy. group t. a form of active transport across a biomembrane in which the transporting molecule is altered in the course of the transport. reciprocal t. t. without demonstrable loss of genetic material. robertsonian t. t. in which the centromeres of two acrocentric chromosomes appear to have fused, forming an abnormal chromosome consisting of the long arms of two different chromosomes with loss of the short arms. A carrier of a balanced robertsonian t. has only 45 chromosomes but near normal chromosomal complement and a clinically normal phenotype; however, he or she is at risk of having a child with unbalanced chromosomal complement. A person with an unbalanced robertsonian t. is trisomic for the long arm of the chromosome. SYN: centric fusion. [W.R.B. Robertson, U.S. geneticist, *1881] unbalanced t. condition resulting from fertilization of a gamete containing a t. chromosome by a normal gamete; if this abnormality is compatible with life, the individual would have 46 chromosomes but a segment of the t. chromosome would be represented three times in each cell and a partial or complete trisomic state would exist.

translucent (trans-loo′sent)
Partially transparent; permitting light to pass through diffusely. [L. translucens, fr. trans- + luceo, to shine through]

transmembrane (trans-mem′bran)
Through or across a membrane.

transmethylase (trans-meth′i-las)
SYN: methyltransferase.

transmethylation (trans′meth-i-la′shun)
Transfer of a methyl group from one compound to another; e.g., l-homocysteine is converted to l-methionine by the transfer to the latter of a methyl group. See methionine synthase.

transmigration (trans-mi-gra′shun)
Movement from one site to another; may entail the crossing of some usually limiting barrier, as in the passage of blood cells through the walls of the vessels (diapedesis). [L. transmigro, pp. -atus, to remove from one place to another] ovular t. the passage of an ovum from one ovary into the fallopian tube of the other side; external ovular t., direct ovular t. occurs when the ovum passes across the pelvic cavity; internal ovular t., indirect ovular t. occurs when the ovum crosses the uterine cavity and so enters the tube of the opposite side.

transmissible (trans-mis′i-bl)
Capable of being transmitted (carried across) from one person to another, as a t. disease, an infectious or contagious disease.

transmission (trans-mish′un)
1. SYN: transfer. 2. The conveyance of disease from one person to another. 3. The passage of a nerve impulse across an anatomic cleft, as in autonomic or central nervous system synapses and at neuromuscular junctions, by activation of a specific chemical mediator that stimulates or inhibits the structure across the synapse. See neurohumoral t.. 4. In general, passage of energy through a material. [L. transmissio, a sending across] duplex t. the passage of impulses in both directions through a nerve trunk. horizontal t. t. of infectious agents from an infected individual to a susceptible contemporary, in contradistinction to vertical t.. iatrogenic t. t. of infectious agents due to medical interference ( e.g., t. by contaminated needles). neurohumoral t. a process by which a presynaptic cell, upon excitation, releases a specific chemical agent (a neurotransmitter) to cross a synapse to stimulate or inhibit the postsynaptic cell. SYN: neurotransmission. transovarial t. passage of parasites or infective agents from the maternal body to eggs within the ovaries; commonly used to describe certain arthropods, to explain the ability of larvae of the next generation to transmit disease pathogens, as with the infection of larval mites or ticks with rickettsiae or viruses. transstadial t. passage of a microbial parasite, such as a virus or rickettsia, from one developmental stage (stadium) of the host to its subsequent stage or stages, particularly as seen in mites. SEE ALSO: transovarial t.. vertical t. 1. t. of a virus ( e.g., RNA tumor virus) by means of the genetic apparatus of a cell in which the viral genome is integrated; 2. for infectious agents in general, t. of an agent from an individual to its offspring, i.e., from one generation to the next. Cf.:horizontal t..

transmural (trans-mu′ral)
Through any wall, as of the body or of a cyst or any hollow structure. [trans- + L. murus, wall]

transmutation (trans-mu-ta′shun)
A change; transformation. SYN: conversion (1) . [L. transmuto, pp. -atus, to change, transmute]

transocular (trans-ok′u-lar)
Across the eye.

transonance (trans′o-nans)
Transmission of a sound arising in one organ through another. [trans- + L. sonans, sounding]

transonic (tran-son′ik)
In ultrasound, describes a region of a relatively unattenuating medium. A distinction should be made between a t. region and an acoustic echo. [trans- + sonic]

transparietal (trans-pa-ri′e-tal)
Through or across a parietal region, area, or structure.

transpeptidase (trans-pep′ti-das)
An enzyme catalyzing a transpeptidation reaction; many proteolytic enzymes ( e.g., trypsin, papain) act as transpeptidases in the course of proteolysis, forming an acylated enzyme as an intermediate in the process; e.g., γ-glutamyl t..

transpeptidation (trans′pep-ti-da′shun)
A reaction involving the transfer of one or more amino acids from one peptide chain to another, as by transpeptidase action, or of a peptide chain itself, as in bacterial cell wall synthesis.

transperitoneal (trans′per-i-to-ne′al)
Through the peritoneum; e.g., denoting a nephrectomy performed by abdominal section.

transphosphatases (trans-fos′fa-tas-ez)
SYN: phosphotransferases.

transphosphorylases (trans-fos-for′i-la-sez)
See phosphotransferases, phosphorylases, kinase.

transphosphorylation (trans′fos-for-i-la′shun)
A reaction involving the transfer of a phosphoric group from one compound to another, often with the involvement of ATP, as by the action of a phosphotransferase or kinase.

transpirable (trans-pi′ra-bl)
Capable of transpiring or being transpired.

transpiration (trans-pi-ra′shun)
Passage of watery vapor through the skin or any membrane. SEE ALSO: insensible perspiration. [trans- + L. spiro, pp. -atus, to breathe] pulmonary t. the passage of water vapor from the blood into the air via the respiratory tract.

transpire (trans-pir′)
To exhale vapor from the skin or respiratory mucous membrane. [trans- + L. spiro, to breathe]

transplacental (tranz-pla-sen′tal)
Crossing the placenta.

transplant (tranz′plant)
1. To transfer from one part to another, as in grafting and transplantation. 2. The tissue or organ in grafting and transplantation. SEE ALSO: graft. [trans- + L. planto, to plant] Gallie t. narrow strips of the femoral fascia lata used for suture material. hair t. autografts of punch biopsies of hair-bearing skin, such as occipital scalp, onto frontal scalp in male pattern alopecia.

transplantar (trans-plan′tar)
Across the sole of the foot; denoting certain muscular fibers or ligamentous structures.


. . . Feedback