Orchiectomy, bilateral
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OCT Definition
Definition
! Optical coherence tomography.
Omeprazole is an antisecretory agent, which is a proton pump inhibitor that is commonly used for suppression of gastric acid output in patients with ! Zollinger-Ellison syndrome; ! gastrinoma.
Octreotide Definition
Oncogene
Octreotide is a chemical compound used in nuclear medicine for localization of ! gastrinoma.
Manfred Schwab DKFZ, Heidelberg, Germany [email protected]
ODC Definition ! Ornithine decarboxylase.
Synonyms *
transforming gene
Definition
Odynophagia Definition Odynophagia is pain during swallowing.
Oligodendrocytoma Definition Oligodendrocytoma is a tumor apparently derived from oligodendrocytic glia; ! brain tumors.
An oncogene is any gene that has the ability to stimulate cellular growth. Oncogene products can transform eukaryotic cells such that they grow in a way analogous to tumor cells. The definition was originally applied to the transforming genes acquired by RNA tumorviruses through ! transduction of oncogenes; today the term is used rather broadly.
Characteristics Oncogenes were originally isolated from ! RNA tumor viruses, where they are responsible for the ability of rapid tumor induction after infection of an animal host. In the viral genome the on-
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Oncogene
cogene was referred to as a viral oncogene or vonc. It was soon established that the v-oncs are actually derived from the genome of the host cell. They are captured by the virus after infection of the cell by a process called transduction (Fig. 1; ! transduction of oncogenes). Transduction appears in a wide range of animal species from chickens to monkeys, it has not been observed in humans. The cellular counterparts, from which the v-oncs are derived, are referred to as proto-oncogene, or c-onc. Proto-oncogenes are normal constituents of the cellular genome and are highly conserved among all eukaryotic organisms. This original rigid definition has softened in subsequent years. Broadly speaking, the term oncogene now includes any gene that has a
growth stimulatory effect on cells, with the result of: * * * *
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conferring sustained cellular multiplication advancement of ! cell cycle progression decreased requirement for ! growth factors focus formation under conditions of cell culture ability of cells to grow under more restricted experimental conditions, such as in soft agar tumorigenic conversion, such as in experimental animals conversion of cells to form tumors that undergo ! metastasis escape from ! apoptosis.
The precursors of oncogenes (proto-oncogenes) are present in their normal structure
Oncogene. Fig. 1 ± Model for the transduction by retroviruses. The process begins when the provirus of a
retrovirus integrates into the vicinity of a cellular oncogene. The characteristic `long terminal repeats' (LTR) are drawn as black and white boxes. A deletion enables the c-onc and the provirus to fuse into a single genetic unit, one of the proviral LTR plus regions of both the provirus and the c-onc , are deleted. Transcription from the hybri
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