Medical Dictionary

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chromonema, pl .chromonemata (kro-mo-ne′ma, -ma-ta)
The coiled filament in which the genes are located, which extends the entire length of a chromosome and exhibits an intensely positive Feulgen test for DNA. SYN: chromatic fiber. [chromo- + G. nema, thread]

chromonychia (kro-mo-nik′e-a)
Abnormality in the color of the nails. [chromo- + G. onyx (onych-), nail]

chromopectic (kro-mo-pek′tik)
SYN: chromatopectic.

chromopexis (kro-mo-pek′sis)
SYN: chromatopexis.

chromophil, chromophile (kro′mo-fil, kro′mo-fil)
1. SYN: chromophilic. 2. A cell or any histologic element that stains readily. SYN: chromatophil (2) . 3. SYN: chromaffin. [chromo- + G. phileo, to love]

chromophilia (kro-mo-fil′e-a)
The property possessed by most cells of staining readily with appropriate dyes. SYN: chromatophilia. [chromo- + G. phileo, to love]

chromophilic, chromophilous (kro-mo-fil′ik, -mof′i-lus)
Staining readily; denoting certain cells and histologic structures. SYN: chromatophil (1) , chromatophilic, chromatophilous, chromophil (1) , chromophile.

chromophobe (kro′mo-fob)
Resistant to stains, staining with difficulty or not at all; denoting certain degranulated cells in the anterior lobe of the pituitary gland. SYN: chromophobic. [chromo- + G. phobos, fear]

chromophobia (kro-mo-fo′be-a)
1. Resistance to stains on the part of cells and tissues. 2. A morbid dislike of colors. SYN: chromatophobia. [chromo- + G. phobos, fear]

chromophobic (kro-mo-fo′bik)
SYN: chromophobe. [chromo- + phobos, fear]

chromophore (kro′mo-for)
The atomic grouping upon which the color of a substance depends. SYN: chromatophore (3) , color radical. [chromo- + G. phoros, bearing]

chromophoric, chromophorous (kro-mo-for′ik, -mof′or-us)
1. Relating to a chromophore. 2. Producing or carrying color; denoting certain microorganisms.

chromophototherapy (kro′mo-pho′to-thar′a-pe)
SYN: chromotherapy. [chromo- + photo- + G. therapeia, medical treatment]

chromoplast (kro′mo-plast)
A plastid filled with carotenoid pigments.

chromoplastid (kro-mo-plas′tid)
A pigmented plastid, containing chlorophyll, formed in certain protozoans. [chromo- + G. plastos, formed, + -id (2)]

chromoprotein (kro-mo-pro′ten)
One of a group of conjugated proteins, consisting of a combination of pigment ( i.e., a colored prosthetic group) with a protein; e.g., hemoglobin.

chromosomal (kro′mo-so′mal)
Pertaining to chromosomes.

chromosome (kro′mo-som)
One of the bodies (normally 46 in somatic cells in humans) in the cell nucleus that is the bearer of genes, has the form of a delicate chromatin filament during interphase, contracts to form a compact cylinder segmented into two arms by the centromere during metaphase and anaphase stages of cell divison, and is capable of reproducing its physical and chemical structure through successive cell divisons. In bacteria and other prokaryotes, the c. is not enclosed within a nuclear membrane and not subject to a mitotic mechanism. Prokaryotes may have more than one c.. [chromo- + G. soma, body] accessory c. a supernumerary c. that is not an exact replica of any of the chromosomes in the normal cellular complement. SYN: monosome (1) , odd c., unpaired allosome, unpaired c.. acentric c. a fragment of a c. lacking a centromere and unable to attach to the mitotic spindle, therefore unable to take part in the division of a nucleus and randomly distributed in daughter cells. SYN: acentric fragment. acrocentric c. a c. with the centromere placed very close to one end so that the short arm is very small, often with a satellite. bivalent c. a pair of chromosomes temporarily united. Christchurch c. an obsolete term describing an abnormal small acrocentric c. (no. 21 or 22) with complete or almost complete deletion of the short arm; found in cultured leukocytes in some cases of chronic lymphocytic leukemia, also in some normal relatives of patients. derivative c. an anomalous c. generated by translocation. SYN: translocation c.. dicentric c. a c. with two centromeres that may result from reciprocal translocation. double minute chromosomes paired, extrachromosomal elements lacking centromeres, often associated with a drug resistance gene. fragile X c. an X c. with a fragile site near the end of the long arm, resulting in the appearance of an almost detached fragment; demonstrated only under special culture conditions; frequently associated with X-linked mental retardation. See Renpenning syndrome. giant c. 1. SYN: polytene c.. 2. SYN: lampbrush c.. heterotypical c. c. that pairs with an unequal partner, e.g., the X and Y chromosomes. homologous chromosomes members of a single pair of chromosomes. lampbrush c., lamp-brush c. 1. a large c. found in oocytes of certain animals characterized by many fine lateral projections giving the appearance of a test tube brush or lampbrush. 2. multiply looped chromosomal area of the chromatin of some species. SYN: giant c. (2) . late replicating c. a c. (often anomalous) that is shown, e.g., by incorporation of a labeled nucleotide, to undergo delayed duplication preliminary to mitosis; formerly used as a means of distinguishing members of a group of chromosomes. marker c. a c. with cytologically distinctive characteristics. metacentric c. a c. with a centrally placed centromere that divides the c. into two arms of approximately equal length. mitochondrial c. the DNA component of mitochondria, the chief function of which is synthesis of adenosine triphosphate and the management of cellular energy; the c. contains some 16,000 base pairs arranged in a circle. The inheritance is matrilineal, and the mutation rate is unusually high; since each cell contains thousands of copies,s a mutant form may assume an almost continuous gradation as in a galtonian process. Most of the mutations known have their impact on the respiratory chain. nonhomologous chromosomes chromosomes that are not members of the same pair. nucleolar c. a c. regularly associated with a nucleolus. odd c. SYN: accessory c.. Philadelphia c. (Ph1) an abnormally shortened c. 22, formed by translocation of a portion of the long arm of c. 22 to c. 9; found in cultured leukocytes of many patients with chronic granulocytic leukemia. polytene c. a stage of c. division that forms the giant c. found in the salivary gland of dipterous insects; the great width is the result of repeated divisions of the chromonema without subsequent lengthwise separation of the filaments. SYN: giant c. (1) . c. puffs expansions of particular c. regions; sites of RNA syntheses. ring c. a c. with ends joined to form a circular structure. The ring form is abnormal in humans but the normal form of the c. in certain bacteria. sex chromosomes the pair of chromosomes responsible for sex determination. In humans and most animals, the sex chromosomes are designated X and Y; females have two X chromosomes, males have one X and one Y c. In certain birds, insects, and fishes the sex chromosomes are designated Z and W; males have two Z chromosomes, females may have one Z and one W c., or one Z and no W c.. SYN: gonosome. submetacentric c. a c. with the centromere so placed that it divides the c. into two arms of strikingly unequal length. telocentric c. a c. with a terminal centromere; such chromosomes in humans are unstable and arise by misdivision or breakage near the centromere and are usually eliminated within a few cell divisions. translocation c. SYN: derivative c.. unpaired c. SYN: accessory c.. W c., X c., Y c., Z c. sex chromosomes. c. walking sequential isolation of overlapping sequences of DNA ( i.e., clones); with this procedure large regions of the c. can be spanned. SYN: overlap hybridization. yeast artificial chromosomes (YAC) yeast DNA sequences that have incorporated into them very large foreign DNA fragments; the recombinant DNA is then introduced into the yeast by transformation; the use of yeast artificial chromosomes permits the cloning of large genes with their flanking regulatory sequences.

chromosome pairing
The process in synapsis whereby homologous chromosomes align opposite each other before disjoining in the formation of the daughter cell; the apposition permits exchange of genetic material in crossing-over.

chromotherapy (kro-mo-thar′a-pe)
Treatment of disease by colored light. SYN: chromophototherapy.

chromotoxic (kro-mo-tok′sik)
Caused by a toxic action on the hemoglobin, as in c. hyperchromemia, or resulting from the destruction of hemoglobin.

chromotrichia (kro-mo-trik′e-a)
Colored or pigmented hair. [chromo- + G. thrix (trich-), hair]

chromotrichial (kro-mo-trik′e-al)
Pertaining to the coloring of hair.

chromotrope (kro′mo-trop)
Any of several dyes containing chromotropic acid and which have the property of changing from red to blue on afterchroming.

chromotrope 2R [C.I. 16570]
A red acid dye used as a counterstain and for staining red blood cells in sections.

chromotropic acid (kro′mo-trop-ik)
Used as a reagent and in chromotropes.

chronaxia (kro-nak′se-a)
SYN: chronaxie.

chronaxie (kro′nak-se)
A measurement of excitability of nervous or muscular tissue; the shortest duration of an effective electrical stimulus having a strength equal to twice the minimum strength required for excitation. SYN: chronaxia, chronaxis, chronaxy. [G. chronos, time, + axia, value]

chronaximeter (kro-nak-sim′e-ter)
An instrument for measuring chronaxie.

chronaximetry (kro-nak-sim′e-tre)
The measurement of chronaxie. [G. chronos, time, + axia, value, + metrein, to measure]

chronaxis (kro-nak′sis)
SYN: chronaxie.

chronaxy (kro′nak-se)
SYN: chronaxie.

chronic (kron′ik)
1. Referring to a health-related state, lasting a long time. 2. Referring to exposure, prolonged or long-term, sometimes meaning also low intensity. 3. The U.S. National Center for Health Statistics defines a c. condition as one of 3 months' duration or longer. [G. chronos, time]

chronicity (kron-is′i-te)
The state of being chronic.

chrono-
Time. [G. chronos]

chronobiology (kron′o-bi-ol′o-je)
That aspect of biology concerned with the timing of biological events, especially repetitive or cyclic phenomena in individual organisms. [chrono- + G. bios, life, + logos, study]

chronognosis (kron-og-no′sis)
Perception of the passage of time. [chrono- + G. gnosis, knowledge]

chronograph (kron′o-graf)
An instrument for graphic measurement and recording brief periods of time. [chrono- + G. grapho, to record]

chronometry (kro-nom′e-tre)
Measurement of intervals of time. [chrono- + G. metron, measure] mental c. study of the duration of mental and behavorial processes.

chrono-oncology (kron′o-on-kol′o-je)
The study of the influence of biological rhythms on neoplastic growth; also used to describe anti-cancer treatment based on the timing of drug administration. [G. chronos, time, + oncology]

chronopharmacology (kron′o-far-ma-kol′o-je)
A branch of chronobiology concerned with the effects of drugs upon the timing of biological events and rhythms, and the relation of biological timing to the effects of drugs.

chronophobia (kron′o-fo′be-a)
Morbid fear of the duration or immensity of time.

chronophotograph (kron-o-fo′to-graf)
A photograph taken as one of a series for the purpose of showing successive phases of a motion.

chronotaraxis (kron′o-ta-rak′sis)
Distortion or confusion of the sense of time. [chrono- + G. taraxis, confusion]

chronotherapy (kro′no-ther′a- pe)
The practice of administering chemotherapy at certain times of the day that are thought to be optimal for enhanced activity or lessened toxicity. SEE ALSO: chrono-oncology. [chrono- + therapy]

chronotropic (kron′o-trop′ik)
Affecting the rate of rhythmic movements such as the heartbeat.

chronotropism (kron-ot′ro-pizm)
Modification of the rate of a periodic movement, e.g., the heartbeat, through some external influence. [chrono- + G. trope, turn, change] negative c. retardation of movement, especially of the heart rate. positive c. acceleration of movement, especially of the heart rate.

chroococcals (kro-o-kok-alz)
A class of cyanobacteria in which the cells are solitary or colonial. [Chroococcus fr. G. chros, chroos, color, + coccus]

chrys-, chryso-
Gold; corresponds to L. auro-. [G. chrysos]

chrysanthemum-carboxylic acids (kri-san′the-mum-kar-bok′si-lik)
Cyclopropane carboxylic acids substituted in one position by two methyl groups, the other by 2-methyl-1-propenyl (chrysanthemum monocarboxylic acid) or by 3-methoxy-2-methyl-3-oxo-1-propenyl (chrysanthemum dicarboxylic acid methyl ester); these acids, esterified with allethrolone or pyrethrolone, are the allethrins and pyrethrins, respectively.

Chrysaora (kris′-a-or-a)
A genus of the invertebrate phylum Cnidaria that includes the sea nettle. C. quinquecirrha the sea nettle, a jellyfish that can inflict moderate to severe stings. SEE ALSO: jellyfish. SYN: sea nettle.

chrysarobin (kris-a-ro′bin)
An extract of Goa powder; a complex mixure of reduction products of chrysophanic acid, emodin, and emodin monomethyl ether; used locally in ringworm, psoriasis, and eczema. [G. chrysos, gold, + Brazil Ind. araroba, bark]

chrysazine (kris′a-zin)
SYN: danthron.

chrysiasis (kri-si′a-sis)
A permanent slate-gray discoloration of the skin and sclera resulting from deposition of gold in macrophages. SYN: auriasis, aurochromoderma. [G. chrysos, gold]

chrysocyanosis (kris′o-si-a-no′sis)
Pigmentation of skin due to reaction to therapeutic use of gold salts.

chrysoidin (kris′oy-din) [C.I. 11270]
A dye (MW 249) made from aniline, used in histology and as an indicator (changing from orange to yellow at pH 4.0 to 7.0); also employed as a substitute for Bismarck brown. C. citrate and c. thiocyanate are used as antiseptics.

Chrysomyia (kris-o-mi′ya)
A genus of myiasis-producing fleshflies (family Calliphoridae) with medium-sized metallic-colored adults; includes the Old World screw worm, C. bezziana (sometimes called Cochliomyia bezziana), which is a primary invader, comparable to Cochliomyia hominivorax, the New World screw worm fly, whereas C. megacephala is an Old World equivalent to Cochliomyia macellaria, both being secondary or saprophytic invaders. [G. chrysos, gold, + myia, fly]

Chrysops (kris′ops)
The deerfly, a genus of biting flies with about 80 North American species, characterized by a splotched wing pattern; C. discalis is a vector of Francisella tularensis in the U.S.; C. dimidiatus and C. silaceus are the principal vectors of Loa loa in west Africa. [G. chrysos, gold, + ops, eye]

Chrysosporium parvum (kris-o-spor′e-um par′vum)
Former name for Emmonsia parva.

chrysotherapy (kris-o-thar′a-pe)
Treatment of disease by the administration of gold salts. SYN: aurotherapy. [G. chrysos, gold]

chunking (chunk′ing)
The process within short-term memory of combining disparate items of information so that they take up as little as possible of the limited space in short-term memory; e.g., combining into one percept the three individual letters making up the word “cat”.

Churg
Jacob, U.S. pathologist, *1910. See C.-Strauss syndrome.

chutta (chut′a)
Cancer of the roof of the mouth developing in Asians who smoke cigars with the lighted end inside the mouth. A similar association has been reported from South America and Sardinia.

Chvostek
Franz, Austrian surgeon, 1834–1884. See C. sign.

chyl-
See chylo-.

chylangioma (ki-lan-je-o′ma)
A mass of prominent, dilated lacteals and larger intestinal lymphatic vessels. [chyl- + G. angeion, vessel, + -oma, tumor]

chylaqueous (ki-la′kwe-us)
Referring to watery chyle. [chyl- + L. aqua, water]

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