| Lens is an indispensable part of the optical system, as well as an important intermediate to the refraction. The maintenance of its transparence plays an important role in maintaining the normal optic-function. The manner of lens development is unique. Posterior epithelial cells elongate and eventually fill the lumen of the vesicle. They then differentiate to form primary fibre cells under the influence of growth factors and start crystalline synthesis. The anterior epithelial cells in the pre-equatorial region migrate to the equator and then elongate both along the posterior capsule and the apical anterior epithelial cells building up layers of new cells from the equator. As they elongate, these secondary fibre cells synthesis a full complement of crystallins, before losing their cell organelles and nuclei. The degeneration of the organelles ensures no absorption or scattering of light but in exchange makes these cells dependent on glycolysis for energy production. The absense of cell nuclei, of DNA and RNA means that the fibre cells are unable torenew their proteins or replace damaged proteins. This unique feature makes the interior structures somewhat dependent. They must rely on the exterior in order to maintain their own stability and to conduct metabolism of the toxicant. On the other hands, the lens, by its unique anatomical location, is continuously exposed to a stressful environment. The lens has no direct blood supply, thus essential biologically important molecules such as oxygen or amino acids are limited, while waste products such as toxins or inflammatory substances remain in close proximity for extended periods of time. Therefore, the lens needs continuous protection against microinvironmentally induced stress. Without such protection lens proteins could degrade causing cataract.Blunt trauma is quite frequent in clinic. The type of complications included: hyphema, iris sphincter tears, iridodialysis, , angle recession, secondary glaucoma, lens dislocation, traumatic cataract, myopia, vitreal hemorrhage, choroidal rupture, retinal tear or detachment, or even globe rupture. The author retrospective analysis of 417 inpatients of the university-eye-hospital Erlangen from 1985-1995 with ocular contusion or globe rupture (EOCR-Erlangen Ocular Contusion -Registry), they found ocular trauma is the cause of every third enucleation, blunt injuries belong to the most frequent causes, 10% of the patients were traumatic cataract. The other study found ocular trauma was the leading cause of noncongenital unilateral blindness in children under 20 years old. The most frequent complication was traumatic cataract in blunt trauma. The most frequent complication was traumatic cataract in blunt trauma. Traumatic cataract is common in clinic, yet there are also cases in which the opacification of lens doesn't worsen and sometimes even becomes transparent again. How lens responses to the stress is essential for the understanding of lens transparency.The heat shock response is a conserved, immediate but transient cellular response to elevated temperatures and other types of injury. It involves the transcriptional activation of a small set of specific gens and a subsequent synthesis ofthe so-called heat shock proteins( HSPs). Recent studies have shown that a wide variety of stresses, including ischemia, oxidative stress, pH extremes, nutrient limitation, osmotic variation, hypoxia, chemotherapeutic agents and noxiouos chemicals, can rapidly induce the expression of the gens for hsp, subsequent induce endogenous protective mechanisms. In mammalian cells, HSPs are commonly classified according to their size, for example, HSP90, HSP70, HSP60, HSP20 to HSP30 KDa(small HSP). Most of HSPs are constructive proteins, only parts of them can be induced by stress. Some studies have shown cataract is related with the abnormal of HSPs, but there is little study on the mechanism of traumatic cataract. Based on the establish of contusion cataract model, this study was designed to investigate the dynamic expression of hsp70 and hsp27 in lens...
|
PDF Full Text Request