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mondofacto - Online Medical Dictionary Category: Health and Medicine > Medical Dictionary Date & country: 26/01/2008, UK Words: 116197

opossum encephalitis
Encephalitis of opossum caused by Chlamydia psittaci. ... (05 Mar 2000) ...

opossums
Marsupials of the family didelphidae. Opossums are common, omnivorous, largely nocturnal and arboreal mammals, grow to about three feet in length, including the scaly prehensile tail, have coarse grayish fur mingled with whitish hairs, and have an abdominal pouch in which the young are carried at birth. (webster, 3d ed) ... (12 Dec 1998) ...

Oppenheim, Hermann
<person> Berlin neurologist, 1858-1919. ... See: Oppenheim's disease, Oppenheim's reflex, Oppenheim's syndrome, Ziehen-Oppenheim disease. ... (05 Mar 2000) ...

Oppenheim's disease
Synonym for amyotonia congenita ... Atonic pseudoparalysis of congenital origin (neither familial nor hereditary), observed especially in infants and characterised by absences of muscular tone only in muscles innervated by the spinal nerves. ... Synonym: congenital atonic pseudoparalysis, myatonia congenita, Oppenheim's disease, Oppenheim's syndrome. …

Oppenheim's reflex
Extension of the toes induced by scratching of the inner side of the leg or by following sudden flexion of the thigh on the abdomen and the leg on the thigh; a sign of cerebral irritation. ... (05 Mar 2000) ...

Oppenheim's syndrome
Synonym for amyotonia congenita ... Atonic pseudoparalysis of congenital origin (neither familial nor hereditary), observed especially in infants and characterised by absences of muscular tone only in muscles innervated by the spinal nerves. ... Synonym: congenital atonic pseudoparalysis, myatonia congenita, Oppenheim's disease, Oppenheim's syndrome. …

oppilation
Obstruction or closing of the pores. ... Origin: L. Oppilatio, fr. Op-pilo (obp-), pp. -atus, to stop up, fr. Pilo, to ram down ... (05 Mar 2000) ...

oppilative
Obstructive to any secretion. ... (05 Mar 2000) ...

opponens
A name given to several muscles of the fingers or toes, by the action of which these digits are opposed to the others. The opponens muscles of the hands act at the carpometacarpal joints, cupping the palm; this enables flexion at the metacarpophalangeal joints to oppose the thumb to the small finger or vice versa. Although comparable muscles in the …

opponens digiti minimi
<anatomy, muscle> Origin, hamulus of the hamate bone and transverse carpal ligament; insertion, shaft of fifth metacarpal; action, 'cups' palm, drawing ulnar side of hand toward centre of palm; nerve supply, ulnar. ... Synonym: musculus opponens digiti minimi, musculus opponens digiti quinti, musculus opponens minimi digiti, opposer muscle of …

opponens pollicis
<anatomy, muscle> Origin, ridge of trapezium and flexor retinaculum; insertion, anterior surface of the full length of the shaft of the first metacarpal bone; action, acts at carpometacarpal joint to 'cup' palm, enabling one to oppose thumb to other fingers; nerve supply, median. ... Synonym: musculus opponens pollicis, opposer muscle of thumb …

opponent colour
Pairs of colour that share colour channels in the retina (red-green, blue-yellow, black-white). ... (05 Mar 2000) ...

opportunistic
1. <microbiology> Denoting a microorganism that does not ordinarily cause disease but that, under certain circumstances (for example impaired immune responses resulting from other disease or drug treatment), becomes pathogenic. ... 2. <disease> Denoting a disease or infection caused by such an organism. ... (18 Nov 1997) ...

opportunistic infections
Infections that occur in persons with weak immune systems due to AIDS, cancer or immunosuppressive drugs such as corticosteroids or chemotherapy. PCP, toxoplasmosis and cytornegalovirus are all examples of OIs. ... (09 Oct 1997) ...

opportunistic pathogen
<microbiology> Pathogenic organism that is often normally a commensal, but which gives rise to infection in immunocompromised hosts. ... (18 Nov 1997) ...

oppose
1. To place in front of, or over against; to set opposite; to exhibit. 'Her grace sat down . . . In a rich chair of state; opposing freely The beauty of her person to the people.' (Shak) ... 2. To put in opposition, with a view to counterbalance or countervail; to set against; to offer antagonistically. 'I may . . . Oppose my single opinion to his.' …

opposer muscle of little finger
Synonym for opponens digiti minimi ... <anatomy, muscle> Origin, hamulus of the hamate bone and transverse carpal ligament; insertion, shaft of fifth metacarpal; action, 'cups' palm, drawing ulnar side of hand toward centre of palm; nerve supply, ulnar. ... Synonym: musculus opponens digiti minimi, musculus opponens digiti quinti, musculus oppo …

opposer muscle of thumb
Synonym for opponens pollicis ... <anatomy, muscle> Origin, ridge of trapezium and flexor retinaculum; insertion, anterior surface of the full length of the shaft of the first metacarpal bone; action, acts at carpometacarpal joint to 'cup' palm, enabling one to oppose thumb to other fingers; nerve supply, median. ... Synonym: musculus opponens …

opposite
1. Placed over against; standing or situated over against or in front; facing; often with to; as, a house opposite to the Exchange. ... 2. Applied to the other of two things which are entirely different; other; as, the opposite sex; the opposite extreme. ... 3. Extremely different; inconsistent; contrary; repugnant; antagonistic. 'Novels, by which th …

opposition
1. The act of opposing; an attempt to check, restrain, or defeat; resistance. 'The counterpoise of so great an opposition.' (Shak) 'Virtue which breaks through all opposition.' (Milton) ... 2. The state of being placed over against; situation so as to front something else. ... 3. Repugnance; contrariety of sentiment, interest, or purpose; antipathy.< …

oppositional disorder
A mental disorder of childhood or adolescence marked by a pattern of disobedient, negativistic, and provocative opposition to authority figures. ... (05 Mar 2000) ...

opposure
Bringing together of tissue during suturing. ... (05 Mar 2000) ...

oppress
1. To impose excessive burdens upon; to overload; hence, to treat with unjust rigor or with cruelty. 'For thee, oppressed king, am I cast down.' (Shak) 'Behold the kings of the earth; how they oppress Thy chosen !' (Milton) ... 2. To ravish; to violate. ... 3. To put down; to crush out; to suppress. 'The mutiny he there hastes to oppress.' (Shak) ... …

opsin
<protein> General term for the apoproteins of the rhodopsin family. ... (18 Nov 1997) ...

opsinogen
A substance that stimulates the formation of opsonin, such as the antigen contained in a suspension of bacteria used for immunization. ... Synonym: opsogen. ... Origin: opsonin + -gen ... (05 Mar 2000) ...

opsiuria
A more rapid excretion of urine during fasting than after a full meal. ... Origin: G. Opsi, late, + ouron, urine ... (05 Mar 2000) ...

opsoclonus
Rapid, irregular, nonrhythmic movements of the eye in horizontal and vertical directions. ... Origin: G. Ops, opos, eye, + klonos, confused motion ... (05 Mar 2000) ...

opsogen
Synonym for opsinogen ... A substance that stimulates the formation of opsonin, such as the antigen contained in a suspension of bacteria used for immunization. ... Synonym: opsogen. ... Origin: opsonin + -gen ... (05 Mar 2000) ...

opsomania
<psychiatry> A longing for a particular article of diet, or for highly seasoned food. ... Origin: G. Opson, seasoning, + mania, frenzy ... (05 Mar 2000) ...

opsonic
Relating to opsonins or to their utilization. ... (05 Mar 2000) ...

opsonic index
A value that indicates the relative content of opsonin in the blood of a person with an infectious disease, as evaluated in vitro in comparison with presumably normal blood; the opsonic index is calculated from the following equation: phagocytic index of normal serum &divide; phagocytic index of test serum = 1 &divide; x, where x represents …

opsonin
<protein> Substance that binds to the surface of a particle and enhances the uptake of the particle by a phagocyte. Probably the most important in mammals derive from complement (C3b or C3bi) or immunoglobulins which are bound through the Fc receptor). ... (18 Nov 1997) ...

opsonisation
A process through which a cell or microbe is treated with opsonin to make it more vulnerable to being engulfed by a phagocyte. Often done simply by incubating particles (e.g. Zymosan) with fresh serum. ... (13 Oct 1997) ...

opsonization
The process by which bacteria are altered in such a manner that they are more readily and more efficiently engulfed by phagocytes. ... (05 Mar 2000) ...

opsonocytophagic
Pertaining to the increased efficiency of phagocytic activity of the leukocytes in blood that contains specific opsonin. ... Origin: opsonin + G. Kytos, a hollow (cell), + phago, to eat ... (05 Mar 2000) ...

opsonometry
Determination of the opsonic index or the opsonocytophagic activity. ... (05 Mar 2000) ...

opsonophilia
The condition in which bacteria readily unite with opsonins, thereby sensitizing them for more effective phagocytosis. ... Origin: opsonin + G. Phileo, to love ... (05 Mar 2000) ...

opsonophilic
Pertaining to, characterised by, or resulting in opsonophilia. ... (05 Mar 2000) ...

optic
Of or pertaining to the eye. ... Origin: Gr. Optikos = of or for sight ... (18 Nov 1997) ...

optic agnosia
Synonym for visual agnosia ... The inability to recognise objects by sight; usually caused by bilateral parieto-occipital lesions. ... Synonym: optic agnosia. ... (05 Mar 2000) ...

optic ataxia
An inability to guide the hand toward an object using visual information; seen in Balint's syndrome. ... (05 Mar 2000) ...

optic atrophy
Atrophy of the optic disk resulting from degeneration of the nerve fibres of the optic nerve and optic tract. ... (12 Dec 1998) ...

optic atrophy, hereditary
An inherited disorder in which optic atrophy is associated with muscle weakness, peroneal muscular atrophy and, in some patients, lancinating pains. In these patients the peripheral sensory neurons are probably affected. ... (12 Dec 1998) ...

optic axis
The axis of the eye connecting the anterior and posterior poles; it usually diverges from the visual axis by five degrees or more. ... Synonym: axis opticus. ... (05 Mar 2000) ...

optic canal
The short canal through the lesser wing of the sphenoid bone at the apex of the orbit that gives passage to the optic nerve and the ophthalmic artery. ... Synonym: canalis opticus, foramen opticum, optic foramen. ... (05 Mar 2000) ...

optic capsule
The concentrated zone of mesenchyme around the developing optic cup; the primordium of the sclera of the eye. ... (05 Mar 2000) ...

optic chiasm
<anatomy> The anatomic point of crossing or decussation of the optic nerve fibres. most of the nerve fibres cross to the opposite side. ... (27 Sep 1997) ...

optic cup
The double-walled cup formed by the invagination of the embryonic optic vesicle; its inner component becomes the sensory layer of the retina, its outer layer, the pigment layer. ... Synonym: caliculus ophthalmicus, ocular cup. ... (05 Mar 2000) ...

optic decussation
Synonym for optic chiasm ... <anatomy> The anatomic point of crossing or decussation of the optic nerve fibres. most of the nerve fibres cross to the opposite side. ... (27 Sep 1997) ...

optic disk
The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve. Because the retina at the optic disk has no photoreceptors there is a corresponding blind spot in the visual field. ... (12 Dec 1998) ...

optic disk drusen
Hyaline bodies occurring in the intra-ocular portion of the optic nerve. They are distinguished from retinal drusen, which lie beneath the retinal pigment epithelium. This disorder is differentiated also from papilledema by the absence of dilated retinal vessels. ... (12 Dec 1998) ...

optic fissure
In the embryo, the temporary gap in the ventral margin of the developing optic cup. ... Synonym: choroid fissure, choroid fissure, choroidal fissure. ... (05 Mar 2000) ...

optic foramen
Synonym for optic canal ... The short canal through the lesser wing of the sphenoid bone at the apex of the orbit that gives passage to the optic nerve and the ophthalmic artery. ... Synonym: canalis opticus, foramen opticum, optic foramen. ... (05 Mar 2000) ...

optic glioma
<oncology, tumour> A tumour of the optic nerve that can result in blindness to the pressure and destruction (caused by the tumour) of the optic nerve. ... There is an association between optic gliomas and neurofibromatosis. Surgical excision or radiation therapy is the general coarse of treatment. ... (27 Sep 1997) ...

optic groove
Synonym for chiasmatic groove ... The groove on the upper surface of the sphenoid bone running transversely between the optic canals bounded anteriorly by the sphenoidal limbus and posteriorly by the tuberculum sellae; forms in relationship to the optic chiasm. ... Synonym: sulcus prechiasmatis, chiasmatic sulcus, optic groove, prechiasmatic sulcus.< …

optic layer
A layer of white matter interspersed with nerve-cell bodies, immediately below the superficial gray layer of the superior colliculus, composed of myelinated fibres originating in the retina and striate cortex, the inner layer of the retina, consisting of the fibres originating from the cells of the ganglionic layer of optic nerve; in their further …

optic lobe
In invertebrate zoology, a lateral lobe of the forebrain in certain arthropods. In vertebrate zoology, either of the corpora bigemina of lower vertebrates. ... (12 Dec 1998) ...

optic nerve
<anatomy, nerve> The optic nerve. The nerve carrying impulses for the sense of sight. ... Projection from the vertebrate retina to the midbrain. Embryologically, a CNS tract rather than a peripheral nerve. Popular experimental preparation for studies of regeneration of retino tectal projections in lower vertebrates and also for studies of glia …

optic nerve diseases
Diseases of the optic nerve. ... (12 Dec 1998) ...

optic nerve drusen
Basophilic, calcareous, laminated acellular bodies within the optic nerve anterior to the scleral lamina cribrosa. ... (05 Mar 2000) ...

optic nerve glioma
<radiology> F = M, child / young adult (75% less than 10 yrs, 90% less than 20 yrs), fusiform, isodense mass, with or without enhancement, rarely calcified associated with neurofibromatosis Cf: optic nerve meningioma ... (12 Dec 1998) ...

optic nerve head
Synonym for optic disk ... The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve. Because the retina at the optic disk has no photoreceptors there is a corresponding blind spot in the visual field. ... (12 Dec 1998) ...

optic nerve hypoplasia
Congenitally small optic disk resulting from failure of development of retinal ganglion cells, with a reduced number of axons; visual impairment may be marked. ... See: de Morsier's syndrome. ... (05 Mar 2000) ...

optic nerve meningioma
<radiology> Female (80%), middle age, (24% occur before 10 yrs, but are associated with neurofibromatosis), tubular, hyperdense mass, intense tramtrack enhancement, ** Cf: optic nerve glioma ... (12 Dec 1998) ...

optic nerve sheath decompression
A venting of the optic nerve sheath into the retrobulbar space, by slitting or by fenestrating the sheath. ... See: optic nerve sheath fenestration. ... (05 Mar 2000) ...

optic nerve sheath fenestration
The cutting of a window in the dura of the optic nerve sheath to relieve papilledema and prevent further loss of optic nerve fibres. ... (05 Mar 2000) ...

optic neuritis
<pathology> Inflammation of the optic nerve. This may occur secondary to a wide variety of causes: multiple sclerosis, posterior uveitis, vascular lesions of the optic nerve (interruption of blood supply to the optic nerve), temporal arteritis, central retinal artery occlusion, methyl alcohol poisoning, drug side effects and acute demyelinati …

optic neuroma
A benign tumour of the optic nerve. ... (12 Dec 1998) ...

optic neuropathy, ischemic
A severely blinding disease resulting from loss of the arterial blood supply to the optic nerve as a result of occlusive disorders of the nutrient arteries. Optic neuropathy is divided into anterior, which causes a pale oedema of the optic disk, and posterior, in which the optic disk is not swollen and the abnormality occurs between the globe and t …

optic papilla
Synonym for optic disk ... The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve. Because the retina at the optic disk has no photoreceptors there is a corresponding blind spot in the visual field. ... (12 Dec 1998) ...

optic part of retina
Synonym for cerebral layer of retina ... The internal layer of the retina containing the neural elements, as distinguished from the outer leaf of the retina, or pigmented layer. ... Synonym: pars optica retinae, neural layer of retina, optic part of retina, stratum cerebrale retinae. ... (05 Mar 2000) ...

optic pit
A congenital structural defect of the optic nerve head. ... (05 Mar 2000) ...

optic placodes
Synonym for lens placodes ... Paired ectodermal placode's that become invaginated to form the embryonic lens vesicles. ... Synonym: optic placodes. ... (05 Mar 2000) ...

optic radiation
The massive, fanlike fibre system passing from the lateral geniculate body of the thalamus to the visual cortex (striate or calcarine cortex, area 17 of Brodmann); the fibres follow the retrolenticular and sublenticular limbs of the internal capsule into the corona radiata but they curve back along the lateral wall of the temporal and occipital hor …

optic recess
A diverticulum extending forward from the anterior part of the third ventricle above the optic chiasm. ... Synonym: recessus opticus. ... (05 Mar 2000) ...

optic sign
<microscopy> For uniaxial materials, by definition, the sign is positive if the value epsilon minus omega is positive, and negative if epsilon - omega is negative. For biaxial materials, the sign is positive if gamma is the acute bisectrix, and negative if alpha is the acute bisectrix, or positive if gamma - beta greater than beta - alpha and …

optic stalk
The constricted proximal portion of the optic vesicle in the embryo; it develops into the optic nerve. ... Pineal stalk, the attachment of the pineal body to the roof of the third ventricle; it contains the pineal recess of the third ventricle. ... Pituitary stalk, a process comprising the tuberal part investing the infundibular stem that attaches th …

optic tectum
<anatomy> A region of the midbrain in which input from the optic nerve is processed. Because the retinally derived neurons of the optic nerve map onto the optic tectum in a defined way, the question of how this specificity is determined has been a long standing problem in cell biology. ... Although there is some evidence for adhesion gradients …

optic tract
The continuation of the optic nerve fibres beyond (behind) the latter's hemidecussation in the optic chiasm; each of the two symmetrical optic tracts is composed of fibres originating from the temporal half of the retina of the ipsilateral eye and a nearly equal number of fibres from the nasal half of the contralateral retina; it forms a compact, s …

optic vesicle
Synonym for ophthalmic vesicle ... In the embryo, one of the paired evaginations from the ventrolateral walls of the forebrain from which the sensory and pigment layers of the retina develop. ... Synonym: vesicula ophthalmica, ocular vesicle, optic vesicle. ... (05 Mar 2000) ...

optical
1. Of or pertaining to vision or sight. 'The moon, whose orb Through optic glass the Tuscan artist views.' (Milton) ... 2. Of or pertaining to the eye; ocular; as, the optic nerves (the first pair of cranial nerves) which are distributed to the retina. ... 3. Relating to the science of optics; as, optical works. ... <optics> Optic angle, a gradu …

optical aberration
Failure of rays from a point source to form a perfect image after traversing an optical system. ... (05 Mar 2000) ...

optical activity
The ability of a material to rotate the plane of polarized light. ... (09 Oct 1997) ...

optical antipode
Synonym for enantiomer ... <chemistry> A pair of chiral isomers (stereoisomers) that are direct, nonsuperimposable mirror images of each other. ... (09 Jan 1998) ...

optical axis
<physics> The line passing through both the centres of curvature of the optical surfaces of a lens, the optical centreline for all the centres of a lens system. ... (09 Oct 1997) ...

optical density
Synonym for absorbance ... 1. <chemistry, investigation> Absorbance is defined as a logarithmic function of the percent transmission of a wavelength of light through a liquid. ... 2. <microbiology> This can be used as a measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule, it is m …

optical diffraction
A technique used to obtain information about repeating patterns. Diffraction of visible light can be used to calculate spacings in the object. ... (18 Nov 1997) ...

optical flat
<microscopy> Usually, a glass or quartz plate or disk, the thickness of which should be at least 1/10 of its diameter. It is ground until any remaining unevenness can be measured only by interferometric methods. Their maximum departure from flatness usually is less than 1/10 of the sodium doublet (589.3 nm). ... (05 Aug 1998) ...

optical illusions
An illusion of vision usually affecting spatial relations. ... (12 Dec 1998) ...

optical image
An image formed by the refraction or reflection of light. ... (05 Mar 2000) ...

optical index
<microscopy> A constant applied to objectives for purposes of comparison. It takes into account the focal length or magnifying power of the lens and also the numerical aperture. It was offered by Nelson and by Coles, but little use has been made of the optical index figure, probably because the equations of the two men differed and the result …

optical iridectomy
<procedure> Iridectomy performed for the purpose of improving vision by making an artificial pupil. ... Peripheral iridectomy, in narrow-angle glaucoma, the surgical removal of a minute portion of the iris at its root; in intracapsular extraction of cataract, removal of one or more minute sections near the peripheral border, leaving the pupill …

optical isomerism
Stereoisomerism involving the arrangement of substituents about an asymmetric atom or atoms (usually carbon) so that there is a difference in the behaviour of the various isomers with regard to the extent of their rotation of the plane of polarised light. ... Compare: stereoisomerism. ... (05 Mar 2000) ...

optical isomers
Isomers differing only in the spatial arrangement of groups around a central atom. Optical isomers rotate the plane of polarized light in different directions. For all biological molecules in which the possibility of optical isomerism exists, only one of the isomers is functional. ... (18 Nov 1997) ...

optical keratoplasty
Transplantation of transparent corneal tissue to replace a leukoma or scar that impairs vision. ... (05 Mar 2000) ...

optical microscope
<instrument, microscopy> A very ambiguous term since all microscopes involve optics, better to specify light, acoustic, X-ray or electron microscope, etc. ... (05 Aug 1998) ...

optical noise
<microscopy> Image defects that become especially conspicuous when the image is enhanced. In video microscopy, includes hot spots, mottle, uneven illumination, etc. ... (05 Aug 1998) ...

optical pachymeter
A lens and/or mirror used to measure corneal thickness. ... (05 Mar 2000) ...

optical righting reflexes
Visual stimuli that enable an animal to maintain the correct position of the head in space, by bringing about movements of the muscles of the neck and limbs. ... (05 Mar 2000) ...

optical rotatory dispersion
The method of measuring the dispersion of an optically active molecule to determine the relative magnitude of right- or left-handed components and sometimes structural features of the molecule. ... (12 Dec 1998) ...