| 释义 |
DictionarySeedegenerationEncyclopediaSeeDegenerationvitreous degeneration
degeneration (de-jen?e-ra'shon) [ de- + generation] Deterioration or impairment of an organ or part in the structure of cells and the substances of which they are a component. See: regenerationdegenerative (de-jen'e-rat?iv, -jen'e-ra-tiv), adjectiveage-related macular degeneration See: macular degenerationamyloid degenerationDegeneration of organs or tissues from amyloid deposits. The deposits are waxy and translucent and have a hyaline appearance. The liver, spleen, and kidneys are usually involved, but any tissue may be infiltrated. ascending degenerationNerve fiber degeneration progressing to the center from the periphery.calcareous degenerationInfiltration of inorganic calcium into tissues. caseous degenerationCheesy alteration of tissues, as seen in tuberculosis. cloudy swelling degenerationA condition in which protein in cells forms minute visible droplets The droplets give the cells a cloudy appearance and may occur in any inflamed tissue. colloid degenerationMucoid degeneration in the protoplasm of epithelial cells.congenital macular degenerationCongenital degeneration of the macula of the eye. corticobasal degenerationA neurological disorder in which brain cells atrophy and die in the basal ganglia and the cortex of the brain. The disease produces symptoms similar to those found in Parkinson's disease but does not respond to parkinsonian medications. cystic degenerationCyst formation accompanying degeneration. descending degenerationNerve fiber degeneration progressing toward the periphery from the original lesion.fatty degenerationDeposit of abnormal amounts of fat in the cytoplasm of cells, or replacement or infiltration of tissues by fat cells. fatty degeneration of the heartFatty infiltration of the heart.fibroid degenerationChange of membranous tissue into fibrous tissue. frontotemporal lobar degenerationPick's disease.granulovacuolar degenerationA pathological finding in the brain cells of some patients with Alzheimer's dementia in which the neuronal cytoplasm is partly replaced by cavities that contain particles resembling grit or sand.gray degenerationDegeneration in myelinated nerve tissue due to chronic inflammation, causing the nerve tissue to turn gray. hepatocerebral degenerationLoss of nerve and supporting cells of the brain from multiple episodes of hepatic encephalopathy or coma. This condition may be caused by Wilson's disease or other insults to the liver, e.g., hepatic coma produced by alcoholic, drug-induced, or viral hepatitis. hepatolenticular degenerationWilson's disease.hyaline degenerationA form of degeneration in which the tissues assume a homogeneous, glassy appearance. It is caused by hyaline deposits replacing musculoelastic elements of blood vessels with a firm, transparent substance that causes loss of elasticity. It is responsible for hardening of the arteries and is often followed by calcification or deposit of lime salts in dead tissue. Calcification also may result in concretions. Synonym: vitreous degeneration; Zenker's degenerationhydropic degenerationPathological change in cells marked by the appearance of water droplets in the cytoplasm.lattice degenerationAtrophy or thinning of the retina at its margins, a common condition that affects about 10% of the population. The condition is usually bilateral and is often asymptomatic although affected persons may complain of seeing sudden flashes of light. It is an occasional cause of retinal detachment. lipoidal degenerationDeposition of fat droplets in cells. macular degeneration, age-related macular degeneration Abbreviation: MD
Loss of pigmentation in the macular region of the retina, usually affecting those over 50. It is a common disease of unknown cause that produces central visual field loss and is the leading cause of permanent visual impairment in the U.S. By age 75, about 15% of Americans are affected. Contributing factors to this disease include a family history of age-related macular degeneration, advancing age, cataract surgery, hyperlipidemia, hypertension, obesity, smoking, and a diet low in carotenoids, vitamin C, vitamin E, and zinc. Persons with Alzheimer's Disease will eventually develop MD but the reverse is not true SymptomsThere are two kinds of macular degeneration: wet and dry. In wet MD, neovascularization intrudes under the retinal pigment epithelium from the choroid, where the new blood vessels may suddenly bleed or leak fluid, distort the normal architecture of the macula, and degrade central visual acuity. The visual loss caused by wet MD is an emergency. In dry MD, the more common and more benign form, hard and soft drusen accumulate beneath the retinal pigment epithelium. They may cause slowly progressive blurring of central vision or may occasionally and gradually lead to wet MD. The central visual loss that marks macular degeneration can make reading, working with the hands, driving, or recognizing people's faces difficult because the center of the visual field is the region of greatest loss of visual acuity (i.e., a central scotoma). Peripheral vision is preserved in this disease. See: visual field for illus TreatmentLaser photocoagulation of new blood vessel membranes can help arrest visual loss in some patients with the exudative form of age-related macular degeneration, changing the wet form to the dry form. However, this form of treatment is complicated by a high rate of recurrence and some immediate visual loss in a scotoma. Other treatments include antiangiogenic drugs, regimens with Vitamins A, C, E, and zinc and copper, photodynamic therapy, radiation therapy, and retinal surgery. Patient careThe Amsler grid, and other testing devices such as a tangent screen, can be used to test patients for visual distortions due to retinal disease, but the validity and reproducibility of Amsler grid testing is poor. Low vision optical aids improve the quality of life for patients who retain good peripheral vision. Affected patients should be referred for visual rehabilitation. mucoid degenerationMucous degeneration.mucous degenerationDeposition of mucus in the connective tissue of organs or in epithelial cells. Synonym: mucoid degeneration; myxomatous degenerationmyxomatous degenerationMucoid degeneration.Nissl degeneration See: Nissl, Franzpigmentary degenerationDegeneration in which affected cells develop an abnormal color.polypoid degenerationFormation of polyp-like growths on mucous membranes. secondary degenerationWallerian degeneration.senile degenerationThe bodily and mental changes that occur during pathological aging.spongy degenerationFamilial demyelination of the deep layers of the cerebral cortex. The affected area has a spongy appearance. Symptoms include mental retardation, enlarged head, muscular flaccidity, and blindness. Death usually occurs before 18 months of age. subacute combined degeneration of spinal cordDegeneration of the posterior and lateral columns of the spinal column. Clinically, paresthesia, sensory ataxia, and sometimes spastic paraplegia are present. The disease is the result of pernicious anemia. vacuolar degenerationSwelling of cells with an increase in the number and size of vacuoles. Synonym: cloudy swellingvitelliform degenerationBest's disease.vitreous degenerationHyaline degeneration.wallerian degenerationThe dying back of the axons of nerves after an insult to nerve tissue, such as a toxic exposure, a metabolic change, trauma, or deprivation of blood supply. The myelin surrounding the axon deteriorates, and the ability of the axon to transmit signals diminishes. Synonym: secondary degenerationwaxy degenerationAmyloid degeneration seen in wasting diseases. Zenker degeneration See: Zenker, Friedrich Albert von |