Medical Dictionary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

onchocercid (ong-ko-ser′kid)
Common name for members of the family Onchocercidae.

Onchocercidae (ong-ko-ser′ki-de)
A family of nematode parasites (superfamily Filarioidea) characterized by production of microfilariae; it includes the genera Onchocerca, Wuchereria, Brugia, Loa, and Mansonella.

onchocercoma (on′ko-ser-ko′ma)
Nodule containing adult worms of Onchocera volvulus. [Onchocerca, taxonomic term, + -oma]

onchocercosis (ong′ko-ser-ko′sis)
SYN: onchocerciasis.

onco-, oncho-
A tumor. [G. onkos, bulk, mass]

Oncocerca (ong-ko-ser′ka)
SYN: Onchocerca.

oncocyte (ong′ko-sit)
A large, granular, acidophilic tumor cell containing numerous mitochondria; a neoplastic oxyphil cell. [onco- + G. kytos, cell]

oncocytoma (ong′ko-si-to′ma)
A glandular tumor composed of large cells with cytoplasm that is granular and eosinophilic because of the presence of abundant mitochondria; occurs uncommonly in the kidney, salivary glands, and endocrine glands. SYN: oxyphil adenoma. [onco- + G. kytos, cell, + -oma, tumor]

oncofetal (ong-ko-fe′tal)
Relating to tumor-associated substances present in fetal tissue, as o. antigens.

oncogene (ong′ko-jen)
1. Any of a family of genes that normally encode proteins involved in cell growth or regulation (e.g., protein kinases, GTPases, nuclear proteins, growth factors) but that may foster malignant processes if mutated or activated by contact with retroviruses. Identified oncongenes include ras, originally noted in bladder tumors, and p53, a mutated version of a gene on chromosome 17 that has been shown to be involved in more than half of all human cancers. Oncogenes can work in concert to produce cancer, and their action may be exacerbated by retroviruses, jumping genes, or inherited genetic mutations. SEE ALSO: tumor suppressor gene. 2. A gene found in certain DNA tumor viruses. It is required for viral replication. SYN: transforming gene. [onco- + gene] Genes whose mutations can permit or induce uncontrolled cellular proliferation and malignant change are of 2 types: protooncogenes and tumor suppressor genes (antioncogenes). Protooncogenes encode proteins that stimulate DNA synthesis and cell division, including peptide growth factors and their cellular membrane receptors; second-messenger cascade proteins, which transmit information from cell membrane to nucleus; and nuclear transcription factors, which control gene expression by binding to DNA. Conversion of a protooncogene to an o. by amplification, translocation, or point mutation can lead to unrestrained cellular proliferation and malignant change. Only 1 copy (allele) of a protooncogene need undergo mutation to induce tumor formation. Protooncogenes are not involved in inherited cancer syndromes, with the exception of the RET protooncogene in multiple endocrine neoplasia. Tumor suppressor genes (antioncogenes), which encode proteins that normally serve to restrain cell proliferation, can be inactivated by point mutation, deletion, or loss of expression. An inherited mutation in 1 copy of a tumor suppressor gene is the basis of most familial predispositions to cancer. Malignant cellular proliferation does not occur until the remaining, functional copy of the gene is inactivated by mutation or by deletion of part or all of its chromosome. In a person born with 2 normal copies of a tumor suppressor gene, both must be inactivated by mutation before tumor formation occurs. BRCA1 and BRCA2, which are associated with familial early-onset breast cancer and ovarian cancer, are tumor suppressor genes. ras o. point mutations first described in rat sarcoma cells that can be shown to have transforming activity in culture as well as in tumorigenesis models in mice; the ras gene family is composed of three closely related genes on three different chromosomes; abnormalities have been identified in a variety of human tumors.

oncogenesis (ong-ko-jen′e-sis)
Origin and growth of a neoplasm. [onco- + G. genesis, production]

oncogenic (ong-ko-jen′ik)
SYN: oncogenous.

oncogenous (ong-koj′e-nus)
Causing, inducing, or being suitable for the formation and development of a neoplasm. SYN: oncogenic.

oncograph (ong′ko-graf)
A recording oncometer, or the recording portion of an oncometer. [onco- + G. graphe, a record]

oncography (ong′kog′ra-fe)
Graphic representation, by means of a special apparatus, of the size and configuration of an organ.

oncoides (ong-koy′dez)
Intumescence or turgescence. [onco- + G. eidos, resemblance]

oncologist (ong-kol′o-jist)
A specialist in oncology. radiation o. SYN: radiotherapist.

oncology (ong-kol′o-je)
The study or science dealing with the physical, chemical, and biologic properties and features of neoplasms, including causation, pathogenesis, and treatment. [onco- + G. logos, study] radiation o. 1. the medical specialty concerned with the use of ionizing radiation in the treatment of disease; 2. the medical specialty of radiation therapy; 3. the use of radiation in the treatment of neoplasms. SYN: radiotherapy, therapeutic radiology.

oncolysis (ong-kol′i-sis)
Destruction of a neoplasm; sometimes used with reference to the reduction of any swelling or mass. [onco- + G. lysis, dissolution]

oncolytic (ong-ko-lit′ik)
Pertaining to, characterized by, or causing oncolysis.

Oncomelania (ong′ko-me-la′ni-a)
A medically important genus of amphibious freshwater operculate snails of the family Hydrobiidae (subfamily Hydrobiinae; subclass Prosobranchiata). In Asia, several subspecies of O. hupensis serve as intermediate hosts of the oriental blood fluke, Schistosoma japonicum. [onco- + G. melas (melan-), black]

oncometer (ong-kom′e-ter)
1. An instrument for measuring the size and configuration of the kidneys and other organs. 2. The measuring, as distinguished from the recording part of the oncograph. [onco- + G. metron, measure]

oncometric (ong-ko-met′rik)
Relating to oncometry.

oncometry (ong-kom′e-tre)
Measurement of the size of an organ.

oncosis (ong-ko′sis)
A condition characterized by the formation of one or more neoplasms or tumors. [G. onkosis, swelling, fr. onkos, bulk, mass]

oncosphere (ong′-ko-sfer)
SYN: hexacanth. [onco- + G. sphaira, sphere]

oncostatin M (onk′o-stat′in em)
An interleukin 6. [onco- + -stat + -in]

oncotherapy (ong-ko-thar′a-pe)
Treatment of tumors.

oncotic (ong-kot′ik)
Relating to or caused by edema or any swelling (oncosis).

oncotomy (ong-kot′o-me)
Rarely used term for incision of an abscess, cyst, or other tumor. [onco- + G. tome, incision]

oncotropic (ong′ko-trop′ik)
Manifesting a special affinity for neoplasms or neoplastic cells. [onco- + G. trope, a turning]

Oncovirinae (ong-ko-vir′i-ne)
Term formerly used to designate a now obsolete subfamily of viruses (family Retroviridae) composed of the RNA tumor viruses that contain two identical plus-stranded RNA molecules. Subgroups are based on antigenicity, host range, and kind of malignancy induced (avian, feline, hamster, or murine leukemia-sarcoma complex; murine mammary tumor virus; primate oncoviruses). Like other retroviruses, they contain RNA-dependent DNA polymerases (reverse transcriptases). An important aspect of these viruses seems to be use of viral reverse transcriptase to make DNA that can be integrated into the DNA of the host cell and will replicate along with cellular DNA. SEE ALSO: retrovirus.

oncovirus (ong′ko-vi′rus)
Term formerly used to describe any virus of the subfamily Oncovirinae. SEE ALSO: oncogenic virus.

ondansetron (on-dan′se-tron)
A serotonin 5-HT3 receptor antagonist used as an antiemetic, particularly in patients undergoing chemotherapy or radiation treatment for cancer.

Ondine
German mythological character. See O. curse.

-one
Suffix indicating a ketone (–CO–) group.

oneiric (o-ni′rik)
1. Pertaining to dreams. 2. Pertaining to the clinical state of oneirophrenia. SYN: oniric. [G. oneiros, dream]

oneirism (o-ni′rizm)
A waking dream state. [G. oneiros, dream]

oneirocritical (o-ni-ro-krit′i-kal)
Rarely used term pertaining to the logic of dreams. [G. oneiros, dream, + kritikos, skilled in judgment]

oneirodynia (o-ni-ro-din′e-a)
Rarely used term for an unpleasant or painful dream. [G. oneiros, dream, + odyne, pain] o. activa SYN: somnambulism (1) .

oneirology (o-ni-rol′o-je)
The study of dreams and their content. [G. oneiros, dream, + logos, study]

oneirophrenia (o-ni-ro-fre′ne-a)
A rarely used term for a state in which hallucinations occur, caused by such conditions as prolonged deprivation of sleep, sensory isolation, and a variety of drugs. [G. oneiros, dream, + phren, mind]

oniomania (o′ne-o-ma′ne-a)
Rarely used term for the morbidly exaggerated need or urge to buy beyond the realistic needs of the individual. [G. onios, for sale, + mania, insanity]

oniric (o-ni′rik)
SYN: oneiric.

-onium
Suffix indicating a positively charged radical; e.g., ammonium, NH4+.

onko-
See onco-.

onlay (on′la)
1. A metal (usually gold) cast restoration of the occlusal surface of a posterior tooth or the lingual surface of an anterior tooth, the entire surface of which is in dentin without side walls; retention in the anterior tooth is by pins and in the posterior by pins and/or boxes in retentive grooves in the buccal and lingual walls. 2. A graft applied on the exterior of a bone. 3. A graft applied to skin in native urethra in hypospadias or stricture repair.

Onodi
Adolf, Hungarian laryngologist, 1857–1920. See O. cell.

onomatomania (on′o-mat-o-ma′ne-a)
An abnormal impulse to dwell upon certain words and their supposed significance, or to frantically try to recall a particular word. [G. onoma, name, + mania, frenzy]

onomatophobia (on′o-mat-o-fo′be-a)
Abnormal dread of certain words or names because of their supposed significance. [G. onoma, name, + phobos, fear]

onomatopoiesis (on′o-mat′o-poy-e′sis)
The making of a name or word, especially to express or imitate a natural sound ( e.g., hiss, crash, boom); in psychiatry, the tendency to make new words of this type is said to characterize some persons with schizophrenia. SEE ALSO: neologism. [G. onoma, name, + poiesis, making]

ontogenesis (on-to-jen′e-sis)
SYN: ontogeny.

ontogenetic, ontogenic (on′to-je-net′ik, -jen′ik)
Relating to ontogeny.

ontogeny (on-toj′e-ne)
Development of the individual, as distinguished from phylogeny, which is evolutionary development of the species. SYN: ontogenesis. [G. on, being, + genesis, origin]

ontology (on-tol′o-je)
A traditional branch of metaphysics that deals with problems of being, existence, inner nature, meaning, etc. It is fundamental to problems involving normality and disease, individuality, responsibility, and the analysis of values. In recent years, it has been slowly assuming a place as a branch of medicine proper.

Onufrowicz
Wladislaus, Swiss anatomist, 1836–1900. See Onuf nucleus.

onyalai (on-i-al′a)
An acute disease affecting natives of Central Africa, characterized by bloody vesicles of the mouth and other mucous surfaces, hematuria, and melena; defective nutrition may be the cause. SYN: akembe, kafindo.

onych-
See onycho-.

onychalgia (on-i-kal′je-a)
Pain in the nails. [onycho- + G. algos, pain]

onychatrophia, onychatrophy (on′i-ka-tro′fe-a, on-ik-at′ro-fe)
Atrophy of the nails. [onycho- + G. atrophia, atrophy]

onychauxis (on-i-kawk′sis)
Marked overgrowth of the fingernails or toenails. [onycho- + G. auxe, increase]

onychectomy (on-i-kek′to-me)
Ablation of a toenail or fingernail. [onycho- + G. ektome, excision]

onychia (o-nik′e-a)
Inflammation of the matrix of the nail. [onycho- + G. -ia, condition] o. maligna acute o. occurring spontaneously in debilitated patients, or in response to slight trauma. o. sicca a condition characterized by brittle nails.

onycho-, onych-
A finger nail, a toenail. [G. onyx, nail]

onychoclasis (on-i-kok′la-sis)
Breaking of the nails. [onycho- + G. klasis, breaking]

onychocryptosis (on′i-ko-krip-to′sis)
SYN: ingrown nail. [onycho- + G. krypto, to conceal]

onychodystrophy (on′i-ko-dis′tro-fe)
Dystrophic changes in the nails occurring as a congenital defect or due to any illness or injury that may cause a malformed nail. [onycho- + G. dys-, bad, + trophe, nourishment]

onychograph (on′i-ko-graf)
An instrument for recording the capillary blood pressure as shown by the circulation under the nail. [onycho- + G. grapho, to write]

onychogryposis (on′i-ko-gri-po′sis)
Enlargement with increased thickening and curvature of the fingernails or toenails. [onycho- + G. gryposis, a curvature]

onychoheterotopia (on′i-ko-het-er-o-to′pe-a)
Abnormal placement of nails.

onychoid (on′i-koyd)
Resembling a fingernail in structure or form. [onycho- + G. eidos, resemblance]

onychology (on-i-kol′o-je)
Study of the nails. [onycho- + G. logos, treatise]

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

. . . Feedback