reaction (re-ak´shun)

1. The response of a muscle or other living tissue or organism to a stimulus. 2. The color change effected in litmus and certain other organic pigments by contact with substances such as acids or alkalies; also the property that such substances possess of producing this change. 3. In chemistry, the intermolecular action of two or more substances upon each other, whereby these substances are caused to disappear, new ones being formed in their place (chemical r.). 4. In immunology, in vivo or in vitro action of antibody on specific antigen, with or without involvement of complement or other components of the immunological system. [L. re-, again, backward, + actio, action]
accelerated r. a response occurring in a shorter time than expected; the cutaneous manifestations occurring during the period between the second and tenth day following smallpox vaccination; because it is intermediate between a primary r. and an immediate r., it is regarded as evidence of some degree of resistance.vaccinoid r;
acid r. 1. any test by which an acid r. is recognized such as the change of blue litmus paper to red; 2. an excess of hydrogen ions over hydroxide ions in aqueous solution indicated by a pH value less than 7 (at 22°C). Cf. dissociation constant of water.
acute phase r. refers to the changes in synthesis of certain proteins within the serum during an inflammatory response; this response provides rapid protection for the host against microorganisms via nonspecific defense mechanisms.
acute situational r. stress r
acute stress r. anxiety r
adverse r. any undesirable or unwanted consequence of a preventive, diagnostic, or therapeutic procedure or regimen.
alarm r. the various phenomena, e.g., stimulated endocrine activity, which the body exhibits as an adaptive response to injury or stress; first phase of the general adaptation syndrome.
aldehyde r. the r. of the indole derivatives with aromatic aldehydes; e.g., tryptophan and p-dimethylaminobenzaldehyde in H2SO4 give a red-violet color useful in assaying proteins for tryptophan content.Ehrlich r;
alkaline r. 1. any test by which an alkaline r. is recognized, such as the change of red litmus paper to blue; 2. an excess of hydroxide ions over hydrogen ions in aqueous solution as indicated by a pH value greater than 7 (at 22°C). Cf. dissociation constant of water. basic r;
allergic r. a local or general r. of an organism following contact with a specific allergen to which it has been previously exposed and sensitized; immunologic interaction of endogenous or exogenous antigen with antibody or sensitized lymphocytes gives rise to inflammation or tissue damage. Allergic r.'s are classified into four major types: type I, anaphylactic and IgE dependent; type II, cytotoxic; type III, immune-complex mediated; type IV, cell-mediated (delayed).hypersensitivity r;
amphoteric r. a double r. possessed by certain fluids which have a combination of acid and alkaline properties.
anamnestic r. augmented production of an antibody due to previous response of the subject to stimulus by the same antigen.
anaphylactic r. (an´a-fI-lak´tik) anaphylaxis
anaplerotic r. See anaplerotic.
antigen-antibody r. (AAR) the phenomenon, occurring in vitro or in vivo, of antibody combining with antigen of the type that stimulated the formation of the antibody, thereby resulting in agglutination, precipitation, complement fixation, greater susceptibility to ingestion and destruction by phagocytes, or neutralization of exotoxin. See also skin test.
anxiety r. a psychological r. or experience involving the apprehension of danger accompanied by a feeling of dread and such physical symptoms as an increase in the rate of breathing, sweating, and tachycardia, in the absence of a clearly identifiable fear stimulus; when chronic, it is called generalized anxiety disorder. See also panic attack.acute stress r;
Arias-Stella r. Arias-Stella phenomenon
arousal r. change in pattern of the brain waves when the subject is suddenly awakened and becomes alert.
Arthus r. 1. Arthus phenomenon 2. arthus-type r.'s, r.'s in man and other species that result from the same basic immunologic (allergic) mechanism which evokes, in the rabbit, the typical Arthus phenomenon. See also immune complex disease.
Ascoli r. a method for confirming the diagnosis of anthrax by means of a precipitin r. which indicates the presence of heat-stable Bacillus anthracis antigen in the extracted tissue.
associative r. a secondary or side r.
basic r. alkaline r
Bence Jones r. the classic means of identifying Bence Jones protein, which precipitates when urine (from patients with this type of proteinuria) is gradually warmed to 45° to 70°C and redissolves as the urine is heated to near boiling; as the specimen cools, the Bence Jones protein precipitates in the indicated range of temperature, and redissolves as the temperature of the specimen becomes less than 30° to 35°C.
Berthelot r. the r. of ammonia with phenol-hypochlorite to give indophenol; the principle is used to analyze ammonia concentration in body fluids.
bi-bi r. a r. catalyzed by a single enzyme in which two substrates and two products are involved; the ping-pong mechanism may be involved in such a r. Cf. mechanism.
Bittorf's r. in cases of renal colic, pain radiating to the kidney upon squeezing the testicle or pressing the ovary.
biuret r. the formation of biuret (NH2CONHCONH2), which gives a violet color due to the r. of a polypeptide of more than three amino acids with CuSO4 in strongly alkaline solution; dipeptides and amino acids (except histidine, serine, and threonine) do not so react; used for the detection and quantitation of polypeptides, or proteins, in biological fluids.
Bloch's r. dopa r
Bordet and Gengou r. See complement fixation.
Brunn r. the increased absorption of water through the skin of the frog when the animal is injected with pituitrin and immersed in water; one of the physiological reactions used to study and classify posterior pituitary polypeptides and their analogues.
Burchard-Liebermann r. a blue-green color produced by acetic anhydride with cholesterol (and other sterols) dissolved in chloroform, when a few drops of concentrated sulfuric acid are added. See Liebermann-Burchard test.
Cannizzaro's r. formation of an acid and an alcohol by the simultaneous oxidation of one aldehyde molecule and reduction of another; a dismutation: 2RCHO -> RCOOH + RCH2OH; when the aldehydes are not identical, this is referred to as a crossed Cannizzaro reaction.
capsular precipitation r. quellung r. (2)
Carr-Price r. the r. of antimony trichloride with vitamin A to yield a brilliant blue color; this r. forms the basis of several quantitative techniques for the determination of vitamin A.
catalatic r. decomposition of H2O2 to O2 and H2O, as in the action of catalase; analogous to peroxidase r.
catastrophic r. the disorganized behavior that is the response to a severe shock or threatening situation with which the person cannot cope.
cell-mediated r. immunological r. of the delayed type, involving chiefly T lymphocytes, important in host defense against infection, in autoimmune diseases, and in transplant rejection. See also skin test.
chain r. a self-perpetuating r. in which a product of one step in the r. itself serves to bring about the next step in the r., and so on. Cf. autocatalysis.
Chantemesse r. a conjunctival r., especially as applied to typhoid.
cholera-red r. a test for cholera vibrio whereby the addition of 3 or 4 drops of sulfuric acid (concentrated, chemically pure) to an 18-hour-old bouillon or peptone culture of the organism produces a color from rose-pink to claret.
chromaffin r. production of a yellow-brown to brown coloration in normal and abnormal cells containing epinephrine and norepinephrine, when fresh tissue slices are placed in a dichromate-chromate mixture overnight; useful for detection of pheochromocytoma (adrenal medulla) and other tumors which produce catecholamines.
circular r. in sensorimotor theory, the tendency of an organism to repeat novel experiences.
cocarde r. , cockade r. See Römer's test.
colloidal gold r. a test (now obsolete) based on precipitation of cerebrospinal fluid protein when mixed with colloidal gold. Abnormalities in this reaction were observed in patients with syphilis, multiple sclerosis, poliomyelitis, and encephalitis.
complement-fixation r. See complement fixation.
consensual r. contraction of the pupil of the fellow eye in consensus with the pupil of the illuminated eye.consensual light reflex, indirect pupillary r;
constitutional r. a generalized r. in contrast to a focal or local r.; in allergy the immediate or delayed response, following the introduction of an allergen, occurring at sites remote from that of injection.
conversion r. conversion hysteria
cross r. a specific r. between an antiserum and an antigen complex other than the antigen complex that evoked the various specific antibodies of the antiserum, due to at least one antigenic determinant that is included among the determinants of the other complex.
cutaneous r. cutireaction
cutaneous graft versus host r. an acute erythematous maculopapular r. with bulla formation in the most severe cases; chronic changes may resemble lichen planus or scleroderma.
cytotoxic r. an immunologic (allergic) r. in which noncytotropic IgG or IgM antibody combines with specific antigen on cell surfaces; the resulting complex initiates the activation of complement which causes cell lysis or other damage, or which, in the absence of complement, may lead to phagocytosis or may enhance T lymphocyte involvement.
Dale r. See Schultz-Dale r.
dark r. in photosynthesis, the fixation of CO2 into carbohydrate, which is independent in place and time of the absorption of light.
decidual r. the cellular and vascular changes occurring in the endometrium at the time of implantation.
r. of degeneration (DR, R.D.) the electrical r. in a degenerated nerve and the muscles supplied by it; characterized by absence of response to both galvanic and faradic stimulus in the nerve and to faradic stimulus in the muscles; the muscles may still respond to galvanic stimulation, but the cathodal closing contraction is greater than the anodal closing contraction, the reverse of normal.
delayed r. a local or generalized response that begins 24 to 48 hours after exposure to an antigen. See cell-mediated hypersensitivity (2), delayed hypersensitivity (2), late r., tuberculin-type hypersensitivity;
depot r. reddening of the skin at the point where the needle entered, in the subcutaneous tuberculin test.
depressive r. depression
dermotuberculin r. Pirquet's test
diazo r. the r. of diazotized sulfanilic acid with bilirubin to form azobilirubin, which forms the basis of quantitating the amount of bilirubin in biological fluids. See van den Bergh's test.Ehrlich's diazo r;
digitonin r. the r. of naturally occurring steroids with 3beta-hydroxyl groups with digitonin, a steroid glycoside, resulting in the formation of an insoluble precipitate; useful in determining the presence of cholesterol and ergosterol.
Dische r. the assay of DNA by means of the blue color formed with diphenylamine in acid (Dische reagent).
dissociative r. r. characterized by such dissociative behavior as amnesia, fugues, sleepwalking, and dream states.
dopa r. a dark staining observed in fresh tissue sections to which a solution of dopa has been applied, presumably due to the presence of dopa oxidase in the protoplasm of certain cells.Bloch's r;
dystonic r. a state of abnormal tension or muscle tone, similar to dystonia, produced as a side effect of certain antipsychotic medication; a severe form, where the eyes appear to roll up into the head, is called oculogyric crisis.
early r. immediate r
echo r. echolalia
Ehrlich r. aldehyde r
Ehrlich's benzaldehyde r. a test for urobilinogen in the urine, by dissolving 2 g of dimethyl-p-aminobenzaldehyde in 100 ml of 5% hydrochloric acid and adding this reagent to urine; a red color in the cold indicates the presence of an excessive amount of urobilinogen.
Ehrlich's diazo r. diazo r
eosinopenic r. reduction in the numbers of circulating eosinophils by ACTH or by adrenal corticoids.
erythrophore r. a reddish coloration (nuptial coloration) caused in certain male fishes (bitterling) by the injection of the gonad test;
eye-closure pupil r. a constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision.Galassi's pupillary phenomenon, Gifford's reflex, lid-closure r., orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon;
false-negative r. an erroneous or mistakenly negative response.
false-positive r. an erroneous or mistakenly positive response.
Fenton r. 1. the use of H2O2 and ferrous salts (Fenton's reagent) to oxidize a-hydroxy acids to a-keto acids or to convert 1,2-glycols to a-hydroxy aldehydes; 2. the formation of OH., OH-, and Fe3+ from the nonenzymatic r. of Fe2+ with H2O2; a r. of importance in the oxidative stress in blood cells and various tissues.
Fernandez r. a delayed hypersensitivity lepromin r., similar to a tuberculin r., at the site of intradermal injection of Dharmendra antigen in a lepromin test.
ferric chloride r. of epinephrine an intense emerald green color in a neutral or slightly acid solution of epinephrine when ferric chloride is added to it; a r. typical of catechols.
Feulgen r. See Feulgen stain.
fight or flight r. the theory advanced by Walter Cannon, that in the autonomic nervous system and the effectors connected with it, the organism in situations of danger requiring either fight or flight is provided with a check-and-drive mechanism that puts it in readiness to meet emergencies with undivided energy output. Also known as the emergency theory.
first-order r. a r. the rate of which is proportional to the concentration of the single substance undergoing change; radioactive decay is a first-order process, defined by the equation -(dN/dt)=kN, where N is the number of atoms subject to decay (reaction), t is time, and k is the first-order decay (reaction) constant, i.e., the fraction of all atoms decaying per unit of time. See also decay constant, order.
fixation r. See complement fixation.
flocculation r. a form of precipitin r. in which precipitation occurs over a narrow range of antigen-antibody ratio, due chiefly to peculiarities of the antibody (precipitin).
focal r. a r. which occurs at the point of entrance of an infecting organism or of an injection, as in the Arthus phenomenon.local r;
Folin's r. the r. of amino acids in alkaline solution with 1,2-naphthoquinone-4-sulfonate (Folin's reagent) to yield a red color; useful for quantitative assay.Folin's reagent;
Forssman r. Forssman antigen-antibody r
Forssman antigen-antibody r. the combination of Forssman antibody with heterogenetic antigen of the Forssman type, as in the agglutination of sheep erythrocytes (which contain Forssman antigen) by serum from a person with infectious mononucleosis which contains Forssman antibody.Forssman r;
fragment r. a r. used to assay the activity of peptidyl transferase.
Frei-Hoffmann r. Frei test
fright r. after section and degeneration of the facial nerve of an animal, the denervated facial muscles contract if the animal is frightened or becomes angry; due to the release of acetylcholine into the circulation.
fuchsinophil r. the property possessed by certain elements, when stained with acid fuchsin, of retaining the stain when treated with picric acid alcohol.
furfurol r. production of a red color on addition of furfurol to a solution of aniline.
galvanic skin r. galvanic skin response
gel diffusion r.'s gel diffusion precipitin tests, under test
Gell and Coombs r.'s See allergic r.
gemistocytic r. a r. to injury resulting in the proliferation of reactive, protoplastic, or gemistocytic astrocytes.
general adaptation r. See general adaptation syndrome.
Gerhardt's r. Gerhardt's test for acetoacetic acid
graft versus host r. (GVHR) clinical and histologic changes of graft versus host disease occurring in a specific organ.
group r. a r. with an agglutinin or other antibody that is common (though usually in varying concentrations) to an entire group of related bacteria, e.g., the coli group.
Gruber's r. Widal's r
Gruber-Widal r. Widal's r
Günning's r. the formation of iodoform from acetone by iodine and ammonia in alcohol.
Haber-Weiss r. the reaction of superoxide (O2. - with hydrogen peroxide to produce molecular oxygen (O2), hydroxide radical (OH. ), and OH-; often, iron catalyzed; a source of oxidative stress in blood cells and various tissues.
harlequin r. sudden blanching of the lower half of the body of an infant lying on its side, leaving the remaining half of the body the normal pink color.
heel-tap r. See heel tap.
hemoclastic r. hemolysis as observed in the laking of the blood.
Henle's r. dark brown staining of the medullary cells of the adrenal bodies when treated with the salts of chromium, the cortical cells remaining unstained.
Herxheimer's r. an inflammatory r. in syphilitic tissues (skin, mucous membrane, nervous system, or viscera) induced in certain cases by specific treatment with Salvarsan, mercury, or antibiotics; believed to be due to a rapid release of treponemal antigen with an associated allergic reaction in the patient.Jarisch-Herxheimer r;
Hill r. that portion of the photosynthesis r. that involves the photolysis of water and the liberation of oxygen and does not include carbon dioxide fixation. It involves the addition of oxidants (quinones or ferricyanide) to chloroplasts; upon illumination, O2 is evolved and the added oxidant is reduced.
homograft r. rejection of an allogenic graft by the host.
hunting r. an unusual r. of digital blood vessels exposed to cold; vasoconstriction is alternated with vasodilation in irregular repeated sequences, in an apparent hunting of equilibrium of skin temperature.hunting phenomenon;
hypersensitivity r. allergic r
id r. an allergic manifestation of candidiasis, the dermatophytoses, and other mycoses characterized by itching, vesicular lesions that appear in response to circulating antigens at sites that are often far distant from the primary fungal lesion itself. See also dermatophytid, -id (1).
r. of identity See gel diffusion precipitin tests in two dimensions, under test.
immediate r. local or generalized response that begins within a few minutes to about an hour after exposure to an antigen to which the individual has been sensitized. See also skin test, wheal-and-erythema r.early r;
immediate hypersensitivity r. an immune response mediated by antibody, usually IgE, which occurs within minutes after a second encounter with an antigen, resulting in the release of histamine and subsequent swelling and vasodilation.
immune r. antigen-antibody r. indicating a certain degree of resistance, usually in reference to the 36- to 48-hour reaction in vaccination against smallpox; because the degree of resistance indicated by the r. is not true immunity and may disappear relatively rapidly there is a tendency to refer to the immune r. as an allergic r.
incompatible blood transfusion r. a syndrome due to intravascular hemolysis of transfused blood by serum antibodies of the recipient, which react with an antigen of the donor red cells; characterized by chills, fever (often with urticaria), backache or muscle cramps, hemoglobinemia, hemoglobinuria, and oliguria, which may result in acute renal failure, DIC, and death.
indirect pupillary r. consensual r
intracutaneous r. , intradermal r. a r. following the injection of antigen into the skin of a sensitive subject, such as in the case of the tuberculin test.
iodate r. of epinephrine a r. dependent upon the oxidation of epinephrine by iodine liberated from iodate, which is decomposed by the hormone; a faint pink color results.
iodine r. of epinephrine a r. resulting from the oxidation of the hormone, a faint pink color appearing upon the addition of iodine.
irreversible r. a r. or response by the tissues to a pathogenic agent characterized by a permanent pathologic change.
Jaffe r. a bright orange-red complex resulting from the treatment of creatinine with alkaline picrate solution; the basis of most routine creatinine tests.
Jarisch-Herxheimer r. Herxheimer's r
Jolly's r. rapid loss of response to faradic stimulation of a muscle with the galvanic response and the power of voluntary contraction retained.myasthenic r;
Kiliani-Fischer r. See Kiliani-Fischer synthesis.
late r. delayed r
lengthening r. in the decerebrate animal, the rather sudden relaxation with lengthening of the extensor muscles when a limb is passively flexed; associated with clasp-knife spasticity.
lepromin r. a delayed hypersensitivity r. at the site of an intradermal injection of a lepromin, such as the Dharmendra antigen or Mitsuda antigen, in a lepromin test; the r.'s, such as the Fernandez or Mitsuda r., are variable, occurring in 48 hours or three to five weeks, but are uniformly negative in lepromatous leprosy, borderline leprosy, and mid-borderline leprosy.
leukemoid r. See leukemoid reaction.
lid-closure r. eye-closure pupil r
Liebermann-Burchard r. See Burchard-Liebermann r.
local r. focal r
local anesthetic r. a toxic r. due to absorption of local anesthetic drug during regional anesthesia, ranging from drowsiness to convulsions and cardiovascular collapse.
Loewenthal's r. the agglutinative r. in relapsing fever.
Lohmann r. the r. catalyzed by creatine kinase.
magnet r. a r. seen in an animal deprived of its cerebellum; when the animal is placed upon its back and the head strongly flexed, the four limbs become flexed in all their joints. Due to stimulation of receptors in the deep layers of the skin, light pressure made upon a toe-pad with the finger causes reflex contraction of the limb extensors; the limb is thus pressed gently against the finger, and when the finger is withdrawn slightly, the experimenter has the sensation that his finger is raising the limb or drawing it out as by a magnet.
Marchi's r. failure of the myelin sheath of a nerve to blacken when submitted to the action of osmic acid.
Mazzotti r. Mazzotti test
Millon r. the r. of phenolic compounds (e.g., tyrosine in protein) with Hg(NO3)2 in HNO3 (and a trace of HNO2) to give a red color.
miostagmin r. a physiochemical immunity test, designed by Ascoli, consisting in determination of the surface tension of an immune serum to which its specific antigen has been added, before and after incubation at 37°C for 2 hours; in a positive r. the surface tension, as measured by the stalagmometer, is lowered.
Mitsuda r. a delayed hypersensitivity lepromin r., in the form of erythematous papular nodules, at the site of intradermal injection of Mitsuda antigen in a lepromin test.
mixed agglutination r. immune agglutination in which the aggregates contain cells of two different kinds but with common antigenic determinants; when used to identify isoantigens, the test cells are exposed to appropriate isoantibody, washed, and then mixed with indicator erythrocytes that combine with free sites on the test cell-attached isoantibody.mixed agglutination;
mixed lymphocyte culture r. See mixed lymphocyte culture test.
monomolecular r. a r. involving a single molecule (e.g., decomposition, intramolecular rearrangement, intramolecular oxidation or reduction), even if a catalytic agent, such as acid or alkali, is present in large excess, on a molecular basis, or is not rate-determining; such r.'s are usually first-order r.'s. Cf. molecularity. unimolecular r;
myasthenic r. Jolly's r
Nadi r. peroxidase r
near r. the pupillary constriction associated with a near vision effort, i.e., with accommodation and convergence.
Neufeld r. Neufeld capsular swelling
neurotonic r. muscular contraction continuing well after cessation of stimulation.
neutral r. pH of 7.00; H+ and OH- ion concentrations equal at 10-7 m at 22°C. Cf. dissociation constant of water.
ninhydrin r. a test for proteins, peptones, peptides, and amino acids possessing free carboxyl and a-amino groups that is based upon the r. with triketohydrinene hydrate; a blue color r. is used to quantitate free amino acids (e.g., after hydrolysis and separation of the amino acids of a protein).triketohydrindene r;
nitritoid r. a severe r. resembling that following the administration of nitrites, sometimes following intravenous administration of arsphenamine or other drugs; consists of flushing of the face, edema of the tongue and lips, vomiting, profuse sweating, a fall in blood pressure, and sometimes death.
r. of nonidentity See gel diffusion precipitin tests in two dimensions, under test.
nuclear r. the interaction of two atomic nuclei or of one such with a subatomic particle, or of the subatomic particles within an atomic nucleus, resulting in a change in the nature of the nuclei concerned or in the energy content of the nuclei or both, usually manifested by transmutation (accompanied by emission of alpha-, beta-, or gamma-rays) or by fission or fusion of the nuclei.
oxidase r. 1. the formation of indol blue when a blood smear containing myeloid leukocytes is treated with a mixture of a-naphthol and p-dimethylaniline sulfate; the myeloid leukocytes contain an oxidase that catalyzes this r., the lymphoid leukocytes do not; 2. in bacteriology, a r. that depends on the presence of certain oxidases in some bacteria that catalyze the transport of electrons between electron donors in the bacteria and an oxidation reduction dye, such as tetramethyl-p-phenylenediamine; the dye is reduced to a blue or black color.
oxidation-reduction r. See oxidation-reduction.
pain r. dilation of the pupil or any other involuntary act occurring in response to a stimulus causing sharp pain anywhere.
Pandy's r. a test to determine the presence of proteins (chiefly globulins) in the spinal fluid, by adding one drop of spinal fluid to 1 ml of solution (e.g., carbolic acid crystals in distilled water, cresol, or pyrogallic acid); the r. varies from a faint turbidity to a dense "milky" precipitate according to the degree of protein content.Pandy's test;
r. of partial identity See gel diffusion precipitin tests in two dimensions, under test.
passive cutaneous anaphylactic r. See passive cutaneous anaphylaxis.
Paul's r. pus is rubbed into a scarification on a rabbit's eye; if the pus is from a variolous or vaccinal pustule a condition of epitheliosis develops in from 36 to 48 hours; the sputum of a smallpox patient is said to cause the same r.Paul's test;
performic acid r. oxidative destruction of the ethylene double bond (-HC=CH-) which is converted to a Schiff-reactive double aldehyde; used to indicate the presence of unsaturated lipids, such as phospholipids and cerebrosides, as well as cystine-rich substances, such as keratin, in tissue sections.
periosteal r. radiographically detectable new subperiosteal bone formed as a r. to soft tissue or osseous disease.
peroxidase r. formation of indophenol blue by the action of an oxidizing enzyme present in certain cells and tissues when they are treated with a solution of a-naphthol and dimethylparaphenylenediamine; by this method, cells of the myelocyte series, which give a positive r., may be distinguished from those of the lymphocyte series, which give a negative r.; endothelial leukocytes give a variable r., probably positive when they have phagocytized the debris of myeloid cells.Nadi r;
phosphoroclastic r. cleavage of C-C bonds that involves phosphate transfer but not, as in phosphorolysis, directly to one of the products; e.g., the decomposition of pyruvate to acetate + CO2, in which Pi is added to ADP to form ATP.
Pirquet's r. Pirquet's test
plasmal r. a histochemical technique that uses mercuric chloride to unmask the aldehyde group of acetalphosphatides and permit Schiff staining.
pleural r. thickening of the pleural stripe on chest radiographs, representing pleuritis, pleural effusion, or pleural fibrosis.
polymerase chain r. (PCR) (po-lim´er-as) an enzymatic method for the repeated copying and amplification of the two strands of DNA of a particular gene sequence. It is widely used in the detection of HIV.In vivo, DNA polymerase facilitates the replication of DNA. During replication, a helical DNA molecule "unzips" and the polymerase moves along one strand mediating the addition of free nucleotides to form complementary base pairs with the nucleotides on the strand. The laboratory technique known as polymerase chain reaction exploits the capacity of DNA polymerase to assemble new DNA. The polymerase is added to a mixture of free nucleotides and primers. Primers are specially prepared units containing both RNA and DNA with a free terminus where the polymerase will react. The short sequence of DNA to be amplified is flanked by two primers. Once the reaction begins, the polymerase churns out multiple copies of the target sequence, which can then be recovered for analysis. PCR is used as a forensic tool, one which is more accurate by one or two magnitudes than DNA fingerprinting.
Porter-Silber r. the basis of the 17-hydroxycorticosteroid test; C-21 adrenocorticosteroids, which contain a dihydroxyacetone group at carbons 19, 20, and 21, react with phenylhydrazine.
Prausnitz-Küstner r. a test for the presence of immediate hypersensitivity in humans; test serum from an atopic individual is injected intradermally into a normal subject; the normal subject is challenged 24-48 hours later with the antigen suspected of causing the immediate hypersensitivity r. in the atopic individual.P-K test;
precipitin r. See precipitin, precipitin test.
primary r. vaccinia
prozone r. See prozone.
psychogalvanic r. , psychogalvanic skin r. galvanic skin response
quellung r. 1. Neufeld capsular swelling 2. if pneumococcal organisms, India ink, and specific antisera are mixed, the antibodies present in the sera will bind to the polysaccharide antigens of the pneumococcal capsule and the capsule will appear more opaque and swollen. This test will identify the organism as being pneumococci as well as the specific capsular types.capsular precipitation r; [Ger. Quellung, swelling]
reversed Prausnitz-Küstner r. the appearance of an urticarial r. at the site of injection when serum containing reaginic antibody is injected into the skin of a person in whom the allergen is already present.
reversible r. a chemical r. that takes place in either direction i.e., from the forward or reverse direction; ionization is such a r., as are r.'s involving racemases, isomerases, mutases, transferases, etc.
Sakaguchi r. guanidines in alkaline solution develop an intense red color when treated with a-naphthol and sodium hypochlorite; a qualitative test for arginine, free or in a protein.
Schardinger r. the reduction of methylene blue to methylene white by formaldehyde is rapidly catalyzed by fresh milk but not by boiled milk, the catalyzing agent being xanthine oxidase (Schardinger's enzyme); an example of oxidation in the absence of O2 with an organic hydrogen acceptor (the dye).
Schultz r. See Schultz stain.
Schultz-Charlton r. the specific blanching of a scarlatinal rash at the site of intracutaneous injection of scarlatina antiserum.Schultz-Charlton phenomenon;
Schultz-Dale r. the contraction of an excised intestinal loop (Schultz) or of an excised strip of virginal uterus (Dale) from a sensitized animal (guinea pig) which occurs when the tissue is exposed to the specific antigen.
serum r. serum sickness
shortening r. the adaptive shortening of the extensor muscles of the limb of a decerebrate animal when the limb is extended after it has been flexed. Cf. lengthening r.
Shwartzman r. Shwartzman phenomenon
skin r. skin test
specific r. the phenomena produced by an agent that is identical with or immunologically related to the one that has already caused an alteration in capacity of the tissue to react.
startle r. startle reflex (1)
Straus r. a diagnostic test for glanders. Male guinea pigs are inoculated intraperitoneally with suspected material; if the glanders organism is present, it will usually set up a necrotizing inflammation in the scrotal sac within a few days and the specific organism can be confirmed bacteriologically.
stress r. an acute emotional r. related to extreme environmental stress.acute situational r;
supporting r.'s described by Magnus, who distinguished two types: positive supporting r.'s , consisting of those reflex muscular contractions whereby the body is supported against gravity; seen in an exaggerated form in the decerebrate animal; negative supporting r.'s , consisting of inhibition of the extensor muscles and unfixing of the joints which thus enable the limb to be flexed and moved into a new position.supporting reflexes;
symptomatic r. an allergic response similar to the original one, but occurring after the use of a test or therapeutic dose of an allergen or atopen.
thermoprecipitin r. the throwing down of a precipitate on the application of heat, as in the case of proteinaceous urine.
Treponema pallidum immobilization r. Treponema pallidum immobilization test
triketohydrindene r. ninhydrin r
type III hypersensitivity r. immune complex disease
unimolecular r. monomolecular r
vaccinoid r. accelerated r
Voges-Proskauer r. a chemical r. used in testing for the production of acetyl methyl carbinol by various bacteria; potassium hydroxide is added to a 24-hour culture in a suitable medium and thoroughly mixed; the treated culture is exposed to air and is observed at intervals of 2, 12, and 24 hours; a positive r. consists of the development of an eosin-like pink color, due to the production of acetylmethylcarbinol, which in the presence of alkali and oxygen is oxidized to diacetyl.
Wassermann r. (W.r.) Wassermann test
Weidel's r. a r. showing the presence of xanthine; a solution of the suspected substance in chlorine water with a little nitric acid is evaporated in a water bath, and then exposed to the vapor of ammonia; the presence of xanthine is indicated when a red or purple color develops.
Weil-Felix r. Weil-Felix test
Weinberg's r. a complement fixation test of the presence of hydatid disease.
Wernicke's r. in hemianopeia, a r. due to damage of the optic tract, consisting in loss of pupillary constriction when the light is directed to the blind side of the retina; pupillary constriction is maintained when light stimulates the normal side. This sign cannot be seen with a bright light because of intraocular scatter onto the seeing half of the retina.Wernicke's sign;
wheal-and-erythema r. the characteristic immediate r. observed in the skin test; within 10 to 15 minutes after injection of antigen (allergen), an irregular, blanched, elevated wheal appears, surrounded by an area of erythema (flare).wheal-and-flare r;
wheal-and-flare r. wheal-and-erythema r
white r. the response seen in many individuals after the skin is lightly stroked with a blunt instrument; it is attributed to capillary action.
whitegraft r. an immune r. to a tissue graft that results in failure of graft vascularization and ensuing rejection.
Widal's r. agglutination r. as applied to the diagnosis of typhoid.Gruber's r., Gruber-Widal r;
xanthoprotein r. a qualitative test for proteins; a yellow product is formed by reacting proteins with hot, concentrated nitric acid.
Yorke's autolytic r. a test for paroxysmal hemoglobinuria; serum is placed in an ice chest and kept at 0°C for 5 to 7 minutes, then in an incubator at 37°C with erythrocytes for 1 hour, at which time, if the r. is positive, hemolysis occurs; if the serum is kept at 1°C for an hour and then placed in the incubator with erythrocytes there is little hemolysis.
zero-order r. a r. that proceeds at a particular rate independently of the concentration of the reactant or reactants.
Zimmermann r. a chemical r. between an alkaline solution of meta-dinitrobenzene and an active methylene group (carbon-16) of 17-ketosteroids; it is the basis of the 17-ketosteroid assay t.; more generally, a r. between methylene ketones and aromatic polynitro compounds in alkaline solutions.Zimmermann test;


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