R

R symbol, roentgen; a symbol used in general chemical formulae to represent an organic radical; Rankine (scale); Réaumur (scale); [L.] remotum (far); respiration; Rickettsia; right.

r symbol for ring chromosome.

ρ rho, small letter; seventeenth letter in the Greek alphabet. Used to designate correlation coefficient in statistics.

R 1929 see azaperone.

R 2028 see fluanisone.

R 4749 see droperidol.

R banding a technique for staining a karyotype using Giemsa stain; produces effects the reverse of G banding.

R conformational state oxyhemoglobin (‘relaxed’) conformational form of hemoglobin.

R-CALF Ranchers-Cattlemen Action Legal Fund; an association of cattle breeders, producers and feeders in the US that developed after disagreement with the NCBA (National Cattlemen’s Beef Association); strong advocate for US beef.

R-on-T phenomenon a form of ventricular arrhythmia in which the electrocardiographic tracing shows premature ventricular complexes occurring in early diastole. It is believed to lead to ventricular fibrillation in most cases.

RA see rheumatoid arthritis, ragocyte.

Ra chemical symbol, radium.

rabbit [rab′it] lagomorph in the family Leporidae. The wild rabbit lives in burrows, is herbivorous and feeds mostly at dawn and dusk. They have great powers of reproduction and have been a serious agricultural pest in some countries. The domestic variety is extensively used in laboratories and there are special varieties for the commercial production of rabbit meat and for pelt and fur production. The genus Sylvilagus includes the large number of species and subspecies of cottontail rabbits of North, Central and South America, while European rabbits are members of Oryctolagus cuniculus. See also the names of domestic varieties: Angora rabbit, Argente, Belgian hare, Beveren, Californian, Dutch, English, Flemish giant, Havana, Himalayan (2), Lop, Netherland dwarf, New Zealand red, New Zealand white, Polish, Rex (2), Russian, sable (2), Satin, Siberian, Silver fox. Other colors include fox, harlequin, lilac, silver, smoke pearl, tan.

brush r. (Sylvilagus bachmani) a lagomorph native to western USA.

r. calicivirus disease see rabbit hemorrhagic disease.

cottontail r. members of the genus Sylvilagus, native to North, Central and South America.

r. fever see tularemia.

r. fibroma virus see Leporipoxvirus, Shope rabbit fibroma.

laboratory r. some specialized strains have been developed to provide a consistent type of rabbit for experimental work in laboratories. The International Index of Laboratory Animals is a reference source for these strains. The most commonly used variety is the New Zealand White.

r. pasteurellosis see rabbit septicemia (below).

r. pox see rabbitpox.

pygmy r. (Brachylagus idahoensis) a small lagomorph native to western USA where it is an endangered species.

rock r. Ochotona princeps; see pika.

r. septicemia a disease of rabbits caused by Pasteurella multocida and characterized by sudden death preceded by fever, dyspnea and nasal discharge. In mild cases there is nasal catarrh and conjunctivitis. Called also snuffles (1).

r. syphilis see spirochetosis (2).

r. tick Haemaphysalis leporispalustris.

volcano r. (Romerolagus diazi) native to very restricted, high elevation volcanic areas in Mexico, it has a small body and small ears. This is an endangered species.

rabbit hemorrhagic disease (RHD) [rab′it hem”-raj′ik] a highly fatal, contagious disease of European rabbits (Oryctolagus cuniculus) but other rabbit species and other wildlife are not susceptible. Caused by rabbit hemorrhagic disease virus (genus Lagovirus, family Caliciviridae); the virus while typical of caliciviruses has not been cultivated. The disease is related to European Brown Hare syndrome but cross-transmission between hares and rabbits of either virus does not occur; spread is by contact, possibly by infected feces, fomites, possibly by spread of carrion by birds, and by recently contaminated insects such as bush flies. After infection rabbits show few clinical signs other than depression and immobility and die after an illness of about 18 hours. Characteristic gross necropsy lesions are enlargement of the liver and spleen and small, focal, pulmonary hemorrhages. There is massive liver necrosis which is believed to be the trigger for disseminated intravascular coagulation. Rabbits less than 6 weeks of age are curiously not susceptible to fatal disease. An effective vaccine is available. A disease notifiable to the OIE (see Table 22). Called also rabbit calicivirus disease, rabbit viral hemorrhagic disease.

rabbitbrush see Tetradymia. Includes spring rabbitbrush (T. glabrata).

rabbitpox [rab′it-poks] a disease of rabbits caused by a poxvirus in the genus Orthopoxvirus. There are typical skin lesions with a systemic illness, ocular and nasal discharge, and a high mortality rate.

rabiate, rabid affected with rabies; pertaining to rabies.

rabid [rab′id] affected by rabies.

rabies [ra′bēz ra′be-ēz] a highly fatal infection caused by a lyssavirus and producing fatal neurologic disease. Rabies virus has a broad host range, but in wildlife the disease persists primarily in bats, which may be true reservoirs, and in terrestrial carnivores. The causative lyssavirus is transmitted in the saliva and the principal method of infection of domestic animals is by a bite. The prinicpal sources for domestic animal infections are in Europe, the red fox, arctic fox, bats and more recently the exotic Asian raccoon dog (Nyctereutesprocyonoides). In North America they are raccoons, striped skunks, red fox, gray fox and bats. Mongoose, jackals and the hyaenas are important sources in Africa and in some countries there is a persistent cycling of infection in wild dogs. In domestic animals, separate furious and dumb (paralytic) forms are described but both commonly occur in the one animal. The syndrome includes an ascending paralysis which may be preceded by a period of mania and aggression and is followed by death. In cattle, bellowing and yawning (voiceless bellowing) occurs and drooling of saliva and pharyngeal paralysis are common in all species. Rabies is one of the most important of the zoonoses because of the inevitably fatal outcome for the infected human. A recombinant vaccinia virus expressing rabies virus glycoprotein G has been used in extensive oral wildlife vaccination campaigns to control rabies in Europe and North America and has been successful in reducing the incidence, especially in Europe, but there are variants of the rabies virus, particularly in skunks, against which the current recombinant vaccina vaccine is ineffective. A disease notifiable to the OIE (see Table 22).

bat r. an infection endemic in bats but at low prevalence. Presence of rabies viral RNA in the saliva of normal bats suggests a subclinical carrier state in some. Bat lyssavirus consists of several genotypes including the widely distributed rabies virus; in Europe, European bat lyssaviruses with two biotypes designated EBLV-1 and EBLV-2; in Africa, Lagos bat virus, Mokola virus and Duvenhage virus; in northern Australia, Australian bat (flying fox) lyssavirus. Rabid bats can transmit the virus to domestic animals and in many countries bats are now the leading cause for administering post-exposure rabies vaccinations to humans.

fixed r. virus see fixed virus.

r. inhibiting substance present in the salivary glands and brain tissue of infected animals and may make the tissue nonlethal for mice by the intracerebral route. It does not interfere with detection of rabies antigen by immunofluorescent staining.

non-terrestrial r. bat rabies.

sylvatic r. that form of the disease transmitted by forest-dwelling animals, particularly foxes and wolves.

rabies-like viruses Mokola, Lagos bat, Duvenhage, European and Australian bat lyssaviruses. So called because they cause rabieslike disease in humans and animals.

R-1: Raccoon. (Procyon lotor). Courtesy of CDC.

rabiform [ra′b-form] resembling rabies.

raccoon (Procyon lotor) a medium-sized procyonid native to North America. They are gray-brown animal with a long, furry tail marked with rings, and a black mask. An important vector for rabies. Called also ’coon’.

r. dog see coonhound.

r. poxvirus a poxvirus that causes typical pox lesions in the raccoon.

r. rabies a major wildlife reservoir and source of human exposure in the southeastern USA.

race 1. a class or breed of animals subordinate to species, i.e. a subspecies; a group of animals having certain characteristics in common, because of a common inheritance. 2. a fenced lane just one animal wide leading to a dipping tank, spray dip, branding chute, drafting gate, etc. 3. see stripe.

racehorse refers usually to Thoroughbred but may also include Standardbred, Trotter.

racemase [ra′s-mās] an enzyme that catalyzes the stereochemical inversion of an asymmetric carbon atom in an optically active substance, such as L-lactic acid.

racemate [ra′s-māt] a racemic compound.

racemethionine [rās″-m-thi′o-nēn] a racemic mixture of d- and L-methionine used as a dietary supplement with lipotropic action.

racemic [ra-se′mik] optically inactive, being composed of equal amounts of dextrorotatory and levorotatory isomers.

racemization [ra″s-m-za′shn] the transformation of one-half of the molecules of an optically active compound into molecules that possess exactly the opposite (mirror-image) configuration, with complete loss of rotatory power because of the statistical balance between equal numbers of dextrorotatory and levorotatory molecules.

racemose [ras′-mōs] shaped like a bunch of grapes.

rachianesthesia [ra″ke-an″es-the′zh] loss of sensation produced by injection of an anesthetic into the spinal canal.

rachicentesis [ra″ke-sen-te′sis] puncture into the lumbar spinal canal. See also spinal puncture.

rachidial, rachidian [ra-kid′e-l] pertaining to the spine.

rachigraph [ra′ke-graf] an instrument for recording the outlines of the spine and back.

rachi(o)- word element. [Gr.] spine.

rachiocampsis [ra″ke-o-kamp′sis] spinal curvature. See lordosis, kyphosis, scoliosis.

rachiomyelitis [ra″ke-o-mi″-li′tis] inflammation of the spinal cord.

rachiotomy [ra″ke-ot′-me] incision of a vertebra or the vertebral column.

rachipagus [ra-kip′-gs] conjoined twins joined at the vertebral column.

rachis [ra′kis] 1. the vertebral column. 2. the shaft of a feather.

rachischisis [ra-kis′k-sis] congenital fissure of the vertebral column.

rachitic [ra-kit′ik] pertaining to rickets.

r. rosary the visible enlargements of the costochondral junctions in rickets.

rachitis [ra-ki′tis] 1. rickets. 2. inflammatory disease of the vertebral column.

rachitogenic [r-kit″o-jen′ik] causing rickets.

rachitomy [r-kit′-me] the surgical or anatomical opening of the spinal canal.

racing contests of speed and endurance with serious biochemical and physiological consequences lessened by adequate training beforehand. See also physical fitness, exertional rhabdomyolysis, heat¹ exhaustion, pulmonary hemorrhage, epistaxis.

r. dogs usually refers to Greyhounds and Whippets, but in some instances may be used to describe the dogs used for endurance sledge racing.

r. injury includes stripping of the tendons of the rear limb by being galloped on, striking the flexor tendons of the forelimb with the toes of the hindlimb (forging or striking), or brushing, (hitting the inside of one lower forelimb by the other). Fractures, tendon ruptures, muscle and tendon sprains are all part of the racing hazard. Fracture or dislocation of cervical vertebrae are an especial hazard in hurdle races and steeplechases.

r. pigeons a variety of pigeons, bred and selected to fly long distances back to their own homes. Races are conducted as time trials with groups of birds being released at specific times and their arrival clocked in.

r. plates lightweight, single-use, horseshoes made of aluminum and with a fullered contact surface; see also horseshoeing.

rack a fast, four beat artificial (taught) gait of horses, similar to the running walk and slow gait, but with more up and down movement. Performed by the five-gaited American saddle horse.

Racosperma see Acacia.

ractopamine hydrochloride a beta-agonist approved by the FDA for use in food-producing animals as a growth promotant to improve leanness and muscle development.

rad [rad] 1. acronym for radiation absorbed dose; a superseded, non-SI unit of measurement of the absorbed dose of ionizing radiation. It corresponds to an energy transfer of 100 ergs per gram of any absorbing material (including tissue). The biological effect of 1 rad of radiation varies with the type of radiation. When the dose is in rem, all types have the same biological effect. Now replaced by the gray. 2. abbreviation for radiograph; used in medical records.

rad. [L.] radix (root).

radar tracking an electronic technique used to follow the flight of birds.

raddle See marking crayon.

Radfordia [rad-for′de-] a genus of mites in the family Myobiidae.

R. affinis found on mice.

R. ensifera found on wild and laboratory rats. May cause sufficient pruritus to result in self-trauma.

radiability [ra″de--bilĩ-te] the property of being readily penetrated by x- or other rays.

radiad [ra′de-ad] toward the radius or radial side.

radial [ra′de-l] 1. pertaining to the radius of the forelimb or to the radial aspect of the forelimb as opposed to the ulnar aspect; pertaining to a radius. 2. radiating; spreading outward from a common center.

r. agenesis a common congenital deformity in animals, particularly in cats. The defect may be uni- or bilateral, causing a marked medial deviation of the lower forelimb. Cats with this condition have been selected to form the basis for a variety known as ’Twisty cats’. Their front legs are greatly reduced, sometimes to useless flippers. They are not recognized by most breed registries and concerns about animal welfare makes it illegal to breed them in some jurisdictions.

r. dysplasia a developmental disorder of the radius and ulna in which growth rates differ and deformities of the limb result.

r. hemimelia absence of the radius.

r. paralysis caused by loss of function of the radial nerve. See Table 14. Manifested by loss of function of extensor muscles and impaired sensory perception in the thoracic limb especially over the dorsum of the paw. Lesions at or distal to the level of the elbow result in difficulty in extending the carpus and foot so that weight may be carried on the dorsum of the foot. Lesions above that level, usually associated with injury to the brachial plexus, also cause an inability to actively extend the elbow (dropped elbow) and the animal cannot bear weight on the limb.

radialis [ra″de-a′lis] [L.] radial.

radiant [ra′de-nt] 1. diverging from a center. 2. emitting rays, as of light or heat.

radiate [ra′de-āt] 1. to diverge or spread from a common point. 2. arranged in a radiating manner.

radiathermy [ra-di″-ther′me] short wave diathermy.

radiatio [ra-de-a′she-o] pl. radiationes [L.] a radiating structure; a collection of nerve fibers connecting different portions of the brain.

R-2: Radial agenesis in a kitten. From Ettinger SJ, Feldman E, Textbook of Veterinary Internal Medicine, 6th Edition. Saunders, 2004.

r. acoustica auditory radiation of the internal capsule in the brain.

radiation [ra″de-a′shn] 1. divergence from a common center. 2. a structure made up of diverging elements, especially a tract of the central nervous system made up of diverging fibers. 3. energy carried by waves or a stream of particles. One type is electromagnetic radiation, which consists of wave motion of electric and magnetic fields. The quantum theory is based on the fact that electromagnetic waves consist of discrete particles, called photons, that have an energy inversely proportional to the wavelength of the wave. In order of increasing photon energy and decreasing wavelength, the electromagnetic spectrum is divided into radio waves, infrared light, visible light, ultraviolet light and X-rays. Another type is the radiation emitted by radioactive materials. Alpha particles are high-energy helium-4 nuclei consisting of two protons and two neutrons, which are emitted by radioisotopes of heavy elements, such as uranium. Beta particles are high-energy electrons, which are emitted by radioisotopes of lighter elements. Gamma rays are high-energy photons, which are emitted along with alpha and beta particles and are also emitted alone by metastable radionuclides, such as technetium-99m. Gamma rays have energies in the X-ray region of the spectrum and differ from X-rays only in that they are produced by radioactive decay rather than by X-ray machines. Radiation with enough energy to knock electrons out of atoms and produce ions is called ionizing radiation. This includes alpha and beta particles and X-rays and gamma rays.

background r. (3) the inescapable radiation received by the entire population due mostly to cosmic radiation, but also due to naturally occurring radioactive materials in the terrestrial environment and to internal isotopes.

characteristic r. (3) nearly homogeneous radiation produced in the target of the X-ray tube when orbital electrons are knocked out and replaced by electrons from outer shells.

corpuscular r. (3) particles emitted in nuclear disintegration, including alpha and beta particles, protons, neutrons, positrons and deuterons.

r. detection (3) special equipment, including Geiger-Miiller tubes and a scintillation crystal, is available to detect radiation which may be accidental, or detect small amounts where this is expected but it needs to be measured in terms of accumulated dose.

electromagnetic r. (3) energy, unassociated with matter, that is transmitted through space by means of waves (electromagnetic waves) traveling in all instances at 3 x 10¹⁰ cm or 186,284 miles per second, but ranging in length from 10¹¹ cm (electrical waves) to 10⁻¹² cm (cosmic rays) and including radio waves, infrared, visible light and ultraviolet, X-rays and gamma rays.

r. exposure (3) means more than the patient being exposed intentionally to an X-ray beam. Technical persons in the vicinity will also be exposed to a much less dangerous but perniciously cumulative load of radiation.

infrared r. (3) the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.75 and 1000 μm. See also infrared.

r. injury (3) is caused by exposure to radioactive material. High doses cause intense diarrhea and dehydration and extensive skin necrosis. Median doses cause initial anorexia, lethargy and vomiting then normality for several weeks followed by vomiting, nasal discharge, dysentery, recumbency, septicemia and a profound pancytopenia. Death is the most common outcome. Chronic doses cause cataract in a few. Congenital defects occur rarely.

interstitial r. (3) energy emitted by radium or radon inserted directly into the tissue.

ionizing r. (3) high-energy radiation, such as X-rays and gamma- rays which react in a similar manner to produce ion pairs or ionization. Gamma-rays are used in the control of growth of tumors and sterilization of food, in which they have some undesirable side-effects, e.g. they destroy the enzymes in meat that cause tenderizing; off-flavors are also a problem.

r. necrosis (3) see radionecrosis.

r. physicist (3) the person responsible for the administration of radiation therapy including estimating the dose required for a treatment, arranging for the dose to be delivered and making arrangements for safety of the patient and staff, and disposing of any residual radioactive material. Technical aspects of the work include computer estimations, preparation of isodose curves, preparation of wedge and compensating filters, and calibration of teletherapy equipment.

primary r.(3) radiation emanating from the X-ray tube which is absorbed by the subject or passes on through the subject without any change in photon energy.

r. protection (3) includes proper control of emissions from the x- ray machines, proper protective clothing for staff, keeping unnecessary people out of the way while the tube is actually generating its beam, the wearing and regular examination of a dosimeter and the proper storage of radioactive materials or residues.

pyramidal r. (2) fibers extending from the pyramidal tract to the cortex.

scatter r. (3) the scattering of radiation in all directions as a result of interaction between the beam of the X-ray and the patient. See also Compton effect.

secondary r. (3) see scatter radiation (above).

r. sensitivity (3) tissues vary in their sensitivity to the damaging effects of irradiation. The rapidly growing tissues are most susceptible, e.g. the embryo, rapidly growing cancer, gonads, alimentary tract, skin and blood-forming organs.

r. sickness (3) see radiation injury (above).

r. striothalamica (2) a fiber system joining the thalamus and the hypothalamic region.

tegmental r. (2) fibers radiating laterally from the red nucleus (nucleus ruber).

thalamic r. (2) fibers streaming out through the lateral surface of the thalamus, through the internal capsule to the cerebral cortex.

r. therapist (3) a person skilled in radiotherapy. See also radiation therapy (below).

ultraviolet r. (3) the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.39 and 0.18 μm. See also ultraviolet rays.

radiative pertaining to or emanating from radiation.

radical [radĩ-kl] 1. directed to the cause; going to the root or source of a morbid process. 2. a group of atoms that enters into and goes out of chemical combination without change and that forms one of the fundamental constituents of a molecule.

free r. a radical, extremely reactive, and having a very short halflife (10⁻⁵ s or less in an aqueous solution), which carries an unpaired electron. Important in cell signaling processes and for intracellular killing of bacteria; implicated in cell damage associated with aging and diseases including cancer, atherosclerosis, Parkinson’s disease and Alzheimer’s disease.

radicle [radĩ-kl] one of the smaller branches of a vessel or nerve.

radicotomy [radĩ-kot′-me] rhizotomy; division or transection of a nerve root.

radicular [r-dik′u-lr] pertaining to a root or radicle.

radiculitis [r-dik″u-li′tis] inflammation of a spinal nerve root, especially of the portion of the root that lies between the spinal cord and the spinal canal.

radiculoganglionitis [r-dik″u-lo-gang″gle-o-ni′tis] inflammation of the dorsal spinal nerve roots and their ganglia.

radiculomedullary [r-dik″u-lo-med′u-lar″e] affecting the nerve roots and spinal cord.

radiculomeningomyelitis[r-dik″u-lo-m-ning″go-mi″-li′tis] inflammation of the nerve roots, meninges and spinal cord.

radiculomyelopathy [r-dik″u-lo-mi″-lop′-the] disease of the nerve roots and spinal cord.

degenerative r. slowly progressive in adult German shepherd and other breeds of dogs, characterized clinically by paraparesis and truncal ataxia. Now known to be due to a mutation in the superoxide dismutase 1 (DOD1) gene, and therefore likely to be a canine form of amyotrophic lateral sclerosis. See degenerative myelopathy.

radiculoneuritis [r-dik″u-lo-n-ri′tis] inflammation of nerve roots and their attendant peripheral nerves.

radiculoneuropathy [r-dik″u-lo-mi″-lop′-the] disease of the nerve roots and spinal nerves.

radiculopathy [r-dik″u-lop′-the] disease of the nerve roots.

spondylotic caudal r. compression of the cauda equina or other nerve roots due to encroachment upon the spinal canal or intervertebral foraminae of the lumbosacral junction by spondylosis, resulting in pain, lower motor neuron dysfunction of the nerves of the hindlimbs and possibly fecal or urinary incontinence. See also lumbosacral stenosis.

radiectomy [ra″de-ek′t-me] radectomy.

radii lentis [ra′de-i] the lens sutures formed by the union of the ends of the lens fibers on the anterior and posterior aspects of the crystalline lens creating a three-pointed star formation.

radi(o)- word element. [L.] ray, radiation, emission of radiant energy, radium, radius (bone of the forearm); affixed to the name of a chemical element to designate a radioactive isotope of that element.

radio-pulse transmitters small electronic devices which give off a small electronic pulse which is reiterated for very long periods, sufficient for a search to be conducted for the beeper. A valuable tool in wildlife studies.

radioactivation analysis see activation analysis.

radioactive [ra″de-o-ak′tiv] characterized by radioactivity.

r. decay spontaneous decomposition of the nuclei of the atoms of radioactive substances. Measured as the proportion of the atoms in a radionuclide that decompose per unit of time, usually stated as the half-life of that particular isotope.

r. isotope radionuclide. A radioactive nuclide, e.g. radioactive iodine or strontium.

r. tracer see radioactive tracer.

radioactivity [ra″de-o-ak-tiv–te] the quality of emitting or the emission of particulate or electromagnetic radiation as a consequence of the decay of the nuclei of unstable elements, a property of all chemical elements of atomic number above 83, and possible of induction in all other known elements. The chemical elements are made up of atoms, each of which consists of a nucleus around which orbits a cloud of negatively charged electrons. The nucleus itself is made up of two kinds of particles: neutrons, which have no electrical charge; and protons, each of which has a single positive charge. A neutral atom has an equal number of protons and electrons and no electric charge. The atomic number of an element is the number of protons in the nucleus of each of its atoms. The mass number of an element is the sum of the number of protons and neutrons in the nucleus. All of the atoms of a particular element have the same atomic number, but can have different numbers of neutrons. An isotope of a chemical element consists of atoms having the same number of protons, but a different number of neutrons. When an atomic nucleus is unstable it decomposes or decays spontaneously, emitting high-energy particles. The emissions from radioactive decay can consist of electrons (beta particles), or electromagnetic energy in the form of photons, or helium ions (alpha particles). (See also radiation.) The process of decay can produce a product that is itself unstable, in which case it too will decay. The process continues until a stable nuclide is finally formed. The radioactivity of a substance can be measured by determining the rate at which atoms decay in a given period of time. The basic unit of measurement of radioactivity is the becquerel (Bq), which is equal to 1 disintegration per second. The now outdated but possibly still used unit is the curie (Ci), which equals 37 thousand-million disintegrations per second. One- thousandth of a curie is a millicurie; one-millionth is a microcurie. These units of measure are used to calculate the dosage of radioactivity administered for various therapeutic procedures in much the same way that units of measure such as the gram and milligram are used to measure dosages of medications. The halflife of an element is the time necessary for one-half of a given amount of the isotope to decay. Half-lives can range from thousands of millions of years to fractions of a second. The rate at which atomic decay occurs in a particular isotope cannot be altered by any outside force such as temperature, pressure or chemical reaction. The knowledge of the half-life of a particular isotope is essential to the proper handling of the substance for the protection of the medical staff and the animal receiving some form of radiation therapy.

radioallergosorbent test (RAST) [ra″de-o-al″r-go-sor′bnt] a radioimmunoassay for the detection and measurement of specific IgE antibody to a variety of allergens, using antigen fixed in a solidphase matrix and radiolabeled anti-IgE antibody.

radioautograph [ra″de-o-aw′to-graf] autoradiograph.

radioautography autoradiography.

radiobicipital [ra″de-o-bi-sip′i-tl] pertaining to the radius and biceps muscle of the forelimb.

radiobiologist [ra″de-o-bi-ol′-jist] an expert in radiobiology.

radiobiology [ra″de-o-bi-ol′-je] the branch of science concerned with effects of light and of ultraviolet and ionizing radiations on living tissue or organisms. See also radiotherapy.

radiocardiogram [ra″de-o-kahr′de-o-gram] the graphic record produced by radiocardiography.

radiocardiography [ra″de-o-kahr″de-og′r-fe] graphic recording of variation with time of the concentration, in a selected chamber of the heart, of a radioactive isotope, usually injected intravenously.

radiocarpal [ra″de-o-kahr′pl] pertaining to the radius and carpus.

r. joint see antebrachiocarpal

radiochemicals radioactive chemicals such as the isotopes [¹²⁵I] iodohippurate.

radiochemistry [ra″de-o-kem′is-tre] the branch of chemistry dealing with radioactive materials.

radiocinematograph see photofluorography.

radiocurability responsiveness to treatment with radiotherapy.

radiocurable [ra″de-o-kūr′-bl] curable by radiation.

radiocystitis [ra″de-o-sis-ti′tis] inflammatory tissue changes in the urinary bladder caused by irradiation. Best called radiation cystitis.

radiodense [ra′de-o-dens″] radiopaque.

radiodensity [ra″de-o-den′s-te] the property of being relatively resistant to the passage of radiant energy.

radiodermatitis [ra″de-o-dur″m-ti′tis] a cutaneous inflammatory reaction to exposure to biologically effective levels of ionizing radiation; X-ray dermatitis.

radiodiagnosis [ra″de-o-di″g-no′sis] diagnosis by means of X-rays or gamma rays.

radioelectrocardiogram [ra″de-o-e-lek″tro-kahr′de-o-gram″] the tracing obtained by radioelectrocardiography.

radioelectrocardiograph [ra″de-o--lek″tro-kahr′de-o-graf″] the apparatus used in radioelectrocardiography.

radioelectrocardiography [ra″de-o-e-lek″tro-kahr″de-og′r-fe] the recording of alterations in the electric potential of the heart, with impulses beamed by radio waves from the subject to the recording device by means of a small transmitter attached to the patient.

radioencephalogram [ra″de-o-n-sef′-lo-gram″] a curve showing the passage of an injected tracer through the cerebral blood vessels as revealed by an external scintillation counter.

radioencephalography [ra″de-o-n-sef″-log′r-fe] the recording of changes in the electric potential of the brain without direct attachment between the recording apparatus and the subject, the impulses being beamed by radio waves from the subject to the receiver.

radiofrequency current heating [ra″de-o-fre′kwn-se] a form of heat therapy in which low-frequency electrical current is passed directly through the tissue being treated, usually skin tumors.

radiogold [ra′de-o-gōld″] a radioisotope of gold, especially ¹⁹⁸Au, which has a half-life of 2.7 days and emits gamma and beta radiation. See gold-198.

radiogram [ra′de-o-gram″] radiograph.

radiograph [ra′de-o-graf″] the film produced by radiography.

scout r. see survey radiograph.

radiographer a radiological technologist whose work is the making of diagnostic radiographs. Duties depend on legislative constraints but may include positioning animals for radiological examinations; determining the proper voltage, current and exposure time for each radiograph and adjusting the X-ray equipment; the production of radiographs requested by the veterinarian; developing the X-ray film; and assisting the radiologist in special procedures and in the preparation of radiopaque contrast media.

radiographic [ra″de-o-graf′ik] pertaining to or emanating from radiography.

r. contrast agent see contrast medium.

r. film digestion test a quantitative test for fecal trypsin in which a strip of X-ray film is incubated in an alkaline suspension of feces. Clearing of the film’s gel indicates the prescence of trypsin. Used in the diagnosis of exocrine pancreatic insufficiency.

r. geometry relates to the loss of clarity of the radiographic image as the subject moves further away from the film.

r. interpretation translation of the radiographic image into an explanation of the pathology underlying the abnormalities that are observed.

radiography [ra″de-o-og′r-fe] the making of film records (radiographs) of internal structures of the body by exposure of film specially sensitized to X-rays or gamma rays.

body-section r. a special technique to show in detail images and structures lying in a predetermined plane of tissue, while blurring or eliminating detail in images in other planes; various mechanisms and methods for such radiography have been given various names, e.g. laminagraphy, tomography, etc.

contrast r. the use of means of exaggerating the differences in density of tissues or organs or intraluminal filling defects, usually by the introduction of contrast agents.

digital r. the capture of images in a digital format; see digital radiography.

double contrast r. see double contrast.

intraoral r. small non-screen film is placed in the mouth and x- rays are directed from outside the mouth. Used to assess alveolar bone and roots of teeth.

mucosal relief r. a technique for revealing any abnormality of the intestinal mucosa, involving injection and evacuation of a barium enema, followed by inflation of the intestine with air under light pressure. The light coating of barium on the inflated intestine in the radiograph reveals clearly even small abnormalities.

neutron r. that in which a narrow beam of neutrons from a nuclear reactor is passed through tissues; especially useful in visualizing bony tissue.

scout r. see survey radiograph, straight (2).

serial r. the making of several exposures of a particular area at arbitrary intervals.

spot-film r. the making of localized instantaneous radiographic exposures during fluoroscopy.

stress r. positioning to intentionally place stress on structures being radiographed; most commonly used in the diagnosis of spinal disorders such as atlantoaxial instability, cervical spondylo- myelopathy (wobbler syndrome) and lumbosacral instability.

radiohumeral [ra″de-o-hu′mr-l] pertaining to the radius and humerus.

radioimaging see imaging.

radioimmunity [ra″de-o--mu′n-te] diminished sensitivity to radiation.

radioimmunoassay (RIA) [ra″de-o-im″u-no-as′a] a sensitive assay method used for the measurement of minute quantities of specific antibodies or any antigen, such as hormones or drugs, against which specific antibodies can be raised. An assay for a specific hormone uses a specific antihormone antibody and a radioisotope label.

competitive r. a technique utilizing isotope labeled antigen that competes with unlabeled antigen for binding by a specific antibody. A very sensitive assay, commonly used in detecting trace amounts of drugs.

radioimmunodiffusion [ra″de-o-im″u-no-d-fu′zhn] immunodiffusion conducted with radioisotope-labeled antibodies or antigens.

radioimmunoelectrophoresis [ra″de-o-im″u-no-e-lek″tro-f-re′sis] electrophoresis in which a particular antigen is identified by adding the corresponding radio-labeled antibody and subjecting the gel to autoradiography.

radioimmunosorbent test (RIST) [ra″de-o-im″u-no-sor′bnt] a radioimmunoassay technique for measuring IgE immunoglobulins in serum, using radiolabeled IgE and anti-IgE bound to an insoluble matrix.

radioiodine [ra″de-o-i′o-dīn] any radioactive isotope of iodine.

r. therapy see iodine-131.

r. uptake t. ¹³¹I or ¹²⁵I are used by oral or intravenous administration as a test of thyroidal function.

radioisotope [ra″de-o-i′s-tōp] a radioactive form of an element. A radioisotope consists of unstable atoms that undergo radioactive decay emitting alpha, beta or gamma radiation. Radioisotopes occur naturally, as in the cases of radium and uranium, or may be created artificially. See also radionuclide. Artificial radioisotopes are created by bombarding stable atoms of an element with subatomic particles in a nuclear reactor or in an atom smasher, or cyclotron. When the nucleus of a stable atom is charged by bombarding particles, the atom usually becomes unstable, or radioactive, and is said to be ‘labeled’ or ‘tagged’.

r. organ scanning injection of an isotope and scanning of organs in which the isotope is planned to locate, e.g. radioactive iodine in the thyroid gland.

radiolabeling incorporation of a radioactive element into a compound in order to investigate its metabolism, fate and utilization.

radioligand [ra″de-o-li′gand] a radioisotope-labeled substance, e.g. an antigen, used in the quantitative measurement of an unlabeled substance by its binding reaction to a specific antibody or other receptor site.

radiological [ra″de-o-loj′-kl] pertaining to radiology.

r. diagnosis see radiological diagnosis.

mobile r. apparatus X-ray machines that can be moved but are not portable because of their weight. This is imposed because of the large transformer required to achieve the desired output.

portable r. apparatus can be carried because of the small transformer used. However, the exposure time is prolonged and the image is less clear. The machine is easily dismantled.

r. technologist a health care worker who is skilled in the theory and practice of the technical aspects of the use of X-rays and radioisotopes in the diagnosis and treatment of disease. Radiological technologists can specialize in radiography, radiation therapy or nuclear medicine. See also radiographer, radiation therapist. Called also nuclear medicine technologist.

radiologist [ra″de-ol′-jist] a specialist in radiology.

radiology [ra″de-ol′-je] the branch of science dealing with use of X-rays, radioactive substances, and other forms of radiant energy in diagnosis and treatment of disease.

veterinary r. dealing with the diseases of animals by radiological methods.

digital r. see digital radiography.

radiolucency [ra″de-o-loo′sn-se] the quality of being radiolucent.

radiolucent [ra″de-o-loo′snt] permitting the passage of radiant energy, such as X-ray, yet offering some resistance to it, the representative areas appearing dark on the exposed film.

radiometer [ra″de-om′-tr] 1. an instrument for estimating X-ray quantity. 2. an instrument in which radiant heat and light may be directly converted into mechanical energy. 3. an instrument for measuring the penetrating power of radiant energy.

radiomimetic [ra″de-o-mi-met′ik] producing effects similar to those of ionizing radiations.

radionecrosis, radiation necrosis [ra″de-o-n-kro′sis] tissue destruction due to radiant energy.

radioneuritis [ra″de-o-n-ri′tis] neuritis from exposure to radiant energy.

radionuclide [ra″de-o-noo′klīd] a radioactive nuclide; one that disintegrates with the emission of corpuscular or electromagnetic radiations. Used in diagnosis for whole body or individual organ scanning. See also radioactive isotope, nuclide.

radiopacity [ra″de-o-o-pas′-te] the quality or property of obstructing the passage of radiant energy, such as X-ray, the representative areas appearing light or white on the exposed film.

radiopaque [ra″de-o-pāk′] not permitting the passage of X-ray, such areas appearing light in color on the X-ray film.

radiopathology [ra″de-o-p-thol′-je] the pathology of radiation effects on tissues.

radiopharmaceutical [ra″de-o-fahr″m-soo′t-kl] a radioactive pharmaceutical used for diagnostic or therapeutic purposes. See also radionuclide.

radiophosphorus [ra″de-o-fos′f-rs] either of two radioactive isotopes of phosphorus, ³²P and ³³P; the former, a pure beta emitter, has a half-life of 14.3 days and is used in solution or colloidal form in erythrocyte studies and in the treatment of polycythemia vera and chronic leukemia in humans.

radiopotentiation [ra″de-o-po-ten″she-a′shn] the action of a drug in enhancing the effects of irradiation.

radioprotective agents chemicals that reduce the effects of radiation on tissues; may be useful in radiotherapy because of the differential concentration between normal and target (tumor) tissues following parenteral administration.

radioresistance [ra″de-o-re-zis′tns] resisting the effects of radiation, especially in reference to the treatment of malignancy.

radioresponsive [ra″de-o-re-spon′siv] reacting favorably to irradiation.

radioresponsiveness quality of being radioresponsive.

radioscopy [ra″de-os′k-pe] fluoroscopy.

radiosensitivity [ra″de-o-sen″s-tiv′-te] sensitivity, as of the skin, tumor tissue, etc., to radiant energy, such as X-ray or other radiations.

radiosensitization the application of heat therapy as an adjunct to radiotherapy to increase the radiosensitivity of target cells.

radiotelemetry [ra″de-o-tl-em′-tre] measurement based on data transmitted by radio waves from the subject to the recording apparatus.

radiotherapist [ra″de-o-ther′-pist] a specialist in radiotherapy.

radiotherapy [ra″de-o-ther′-pe] the treatment of disease by ionizing radiation. The purpose of radiation therapy is to deliver an optimal dose of either particulate or electromagnetic radiation to a particular area of the body with minimal damage to normal tissues. The source of radiation may be outside the body of the patient (external radiation therapy) or it may be an isotope that has been implanted or instilled into abnormal tissue or a body cavity. Called also radiation therapy. Modern radiation therapy primarily uses high-energy X-rays or gamma rays with peak photon energies above 1 MeV. This is called ‘supervoltage’ or ‘megavoltage’ therapy. These high voltages are produced by linear accelerators or by cobalt-60 teletherapy units. Megavoltage radiation is more penetrating than lower energy radiation. It produces less damage to the skin at the entry port, is absorbed less in bone, and is scattered less, thus reducing the exposure to tissues outside the X-ray beam. Low-energy X-rays that do not penetrate are used for treatment of superficial skin lesions. Internal radiation therapy can involve the implantation of sealed radiation sources in or near cancerous tissue. Isotopes, such as radium-226, cesium-137, iridium-192 and iodine-125, are introduced either temporarily or permanently into body tissues (interstitial application) or body cavities (intercavitary application). Permanent sources have a short half-life so that the dose received by the patient is limited. Another form of internal radiation therapy is the administration of radioactive materials into the bloodstream or a body cavity. See also radiation, external beam therapy, orthovoltage, brachytherapy.

external beam r. see teletherapy.

fractionated r. the full dose is divided and given as a number of separate small treatments.

intraoperative r. the use of radiotherapy during a surgical procedure, usually in the treatment of diffuse neoplasia that cannot be totally removed by surgical methods alone.

supervoltage r., megavoltage r. the use of energy in excess of 500 keV.

radiothermy short-wave diathermy.

radiotoxemia [ra″de-o-tok-se′me-] toxemia produced by a radioactive substance, or resulting from radiotherapy.

radiotracer [ra″de-o-tra′sr] a radioactive tracer.

radiotranslucent radiolucent.

radiotransparent [ra″de-o-trans-par′nt] permitting the passage of X-rays or other forms of radiation. See also radiolucent.

radiotropic [ra″de-o-tro′pik] influenced by radiation.

radioulnar [ra″de-o-ul′nr] pertaining to the radius and ulna.

r. incongruence relative underdevelopment of the radius results in a step defect between the articular surfaces of the radius and ulna which leads to osteoarthritis of the canine elbow.

radish [rad′ish] see Raphanus. Includes fodder radish (R. sativus), wild radish (R. raphanistrum).

radium (Ra) [ra′de-m] a chemical element, atomic number 88, atomic weight, 226. See Table 4. Radium is highly radioactive and is found in uranium minerals. Radium-226 has a half-life of 1622 years. It and its short-lived decay products emit alpha particles, beta particles and gamma rays. One of the decay products, radon-222, is a radioactive gas. In clinical use, radium is contained in a metal container that stops alpha and beta particles and traps radon. Radium is used in the treatment of malignant diseases, particularly those that are readily accessible, for example, tumors of the eye. In the form of needles or pellets, it can be inserted in the tumorous tissue (interstitial implantation) and left in place until its rays penetrate and destroy malignant cells. It can also be used in the form of plaques applied to the diseased tissue. Large amounts of radium are used as a source of gamma rays, which are capable of deep penetration of matter. See also radiotherapy.

radius [ra′de-s] pl. radii [L.] 1. a line radiating from a center, or a circular limit defined by a fixed distance from an established point or center. 2. one of the two long bones of the forearm that extends from the lateral side of the elbow to the medial side of the wrist or carpus. See also Table 10.

r. curvus syndrome see curvus.

radix [ra′diks] pl. radices [L.] root.

radon (Rn) [ra′don] a chemical element, atomic number 86, atomic weight 222. See Table 4. Radon is a colorless, gaseous, radioactive element produced by the disintegration of radium.

raffinose [raf′-nōs] a crystalline, trisaccharide obtained from cottonseed meal and Australian manna, a substance obtained from a number of eucalypts. Contains dextrose, fructose and galactose. Called also melitose.

Rafinesquia californica toxic plant in the family Asteraceae; causes nitrate–nitrite poisoning; called also California chicory.

rafoxanide [r-fok′s-nīd] a very efficient flukicide which is also effective against Haemonchus contortus and Oestrus ovis. Available for both oral and injectable administration. There is a good safety margin but poisoning can occur in sheep with heavy doses. There is blindness, with degeneration of the optic nerve, recumbency, polypnea, clonic convulsions and death.

Ragamuffin a breed of cat derived from the Ragdoll breed. It has a medium length coat that comes in all colors.

Ragdoll a recently developed breed of cats, derived from Persians, Birmans and Burmese. It is a very large cat with medium to long hair, colored points and blue eyes. When held, it relaxes completely, hence the name.

rage [rāj] 1. a state of violent anger. 2. [Fr.] rabies.

sham r. an outburst of motor activity resembling the outward manifestations of fear and anger, occurring in decorticated animals and in certain pathological conditions in humans.

r. syndrome a syndrome in dogs of sudden episodes of aggression with no obvious provoking stimuli reported in Springer spaniels and Cocker spaniels. Possibly a type of psychomotor seizure since a similar syndrome in people occurs with lesions of the limbic system or temporal lobe. Because of the unpredictable and dangerous nature of the episodes or rage, euthanasia is usually advised. Called also episodic dyscontrol syndrome.

ragged hips defective conformation in a horse characterized by asymmetry, irregularity or ugly prominence of the ilial tuberosities; caused mostly by fractures of the ilium caused by falling.

ragocyte [rag′o-sīt] a cell found in the joints in rheumatoid arthritis; RA cell. Such cells are produced when polymorphonuclear leukocytes ingest aggregated IgG immunoglobulin, rheumatoid factor, fibrin and complement. Rare in dogs.

ragpicker′s disease anthrax.

ragweed [rag′wēd] see Artemisia, a name sometimes used for Senecio but more commonly Ambrosia elatir, or Franseria discolor (white ragweed).

ragwort [rag′wrt] Senecio. Includes marsh ragwort (S. aquaticus), Oxford ragwort (S. squalidus), tansy ragwort (S. jacobea).

rail-out a carcass that has been placed on a special rail in the packing plant so that the USDA inspector can make a more detailed inspection of the carcass without disrupting the flow on the main rail.

railer see realizer.

Raillietia [ri″le-e′she-] a genus of mites in the family Gamasidae.

R. auris found on the ears of cattle.

R. australis found in the ears of wombats.

R. caprae found in the ears of goats.

R-3: Raillietia auris from the ear of a cow. From Krametter-Froetscher R, Leschnik M, Hoegler S, Loewenstein M, Baumgartner W: Occurrence of the ear-mite Raillietia auris in cattle in Austria. Vet J 171:186-188, 2006. Elsevier.