Ultrastructure of the vitreous body of the rabbit

Examination in the scanning and the transmission electron microscope showed three morphologically and structurally different types of cells in the vitreous body of the healthy rabbit eye: 1. cells with numerous cytoplasm processes, whose high metabolic activity is represented by the presence of a large number of organelles and which are capable of synthesizing fibrillar material; 2. elongate cells with a flattened nucleus, with long, narrow cytoplasm processes arising from both their poles and with only a few organelles in their cytoplasm; 3. large spherical cells with structureless contents, whose nucleus and few organelles are situated below the cell membrane. The organized component of the intercellular matter of the rabbit vitreous body is composed of collagen fibrils with a very variable diameter (24-180 nm), The collagen fibrils form the basis of the three-dimensional skeleton of the intercellular matter of the vitreous body.     

Adhesion of the vitreous body to cured polymers

The adhesive activity of several polymers as regard to vitreous body (VB) was examined by drying out the vitreous body on the surface of the materials under study. 3 types of polymers were compared with glass (silicon, polyurethan, polymethylmetacrilate). According to the reduction in adhesive activity as regard to VB the substances were ranged from silicon to glass. The authors believe that the mechanism of VB adhesion to polymers is linked to the absorption of gialuronic acid on their surface, which is part of VB. The above method is suggested for the selection of polymers used in the manufacturing of intraocular lenses.     

Persistent hyperplastic primary vitreous

Persistent hyperplastic primary vitreous (PHPV) is a common congenital developmental anomaly of the eye that results following failure of the embryological, primary vitreous and hyaloid vasculature to regress. It typically presents unilaterally without associated systemic findings. Although the etiology is assumed to be identical in each of its three variants, PHPV is still subclassified into three presentations. The purely anterior presentation of PHPV is also known as persistent tunica vasculosa lentis and persistent posterior fetal fibrovascular sheath of the lens. It occurs in eyes with pathology of the anterior segment. This form typically involves cataract, glaucoma and a retrolenticular membrane. The purely posterior presentation of PHPV is termed falciform retinal septum and ablatio falcicormis congentia. It occurs in eyes with abnormalities confined to the posterior segment such as retinal folds, vitreal stalk, vitreal membranes, macular abnormalities and optic disc abnormalities. A combination of anterior and posterior presentations is the most commonly seen clinical presentation. Case report. We present a case in which an 11-year old male was referred to our office for reevaluation of a large angle esotropia, strabismic and deprivational amblyopia and previously diagnosed PHPV, OD. Conclusion. Without treatment, PHPV can produce recurrent intraocular hemorrhage, secondary glaucoma and eventually require enucleation. Early surgical intervention is necessary to prevent progressive pathologic changes and to obtain the best visual results. Finally, while PHPV is a documented source of leukocoria, clinicians should be aware of differential diagnoses which involve the white pupil (congenital cataract, retinoblastoma, Norrie's disease, retinopathy of prematurity, retinal detachment and Coat's disease).     

Cryo-electron microscopy of vitreous sections

Since the beginning of the 1980s, cryo-electron microscopy of a thin film of vitrified aqueous suspension has made it possible to observe biological particles in their native state, in the absence of the usual artefacts of dehydration and staining. Combined with 3-d reconstruction, it has become an important tool for structural molecular biology. Larger objects such as cells and tissues cannot generally be squeezed in a thin enough film. Cryo-electron microscopy of vitreous sections (CEMOVIS) provides then a solution. It requires vitrification of a sizable piece of biological material and cutting it into ultrathin sections, which are observed in the vitrified state. Each of these operations raises serious difficulties that have now been overcome. In general, the native state seen with CEMOVIS is very different from what has been seen before and it is seen in more detail. CEMOVIS will give its full potential when combined with computerized electron tomography for 3-d reconstruction.     

Review of vitreous islet cryopreservation

Transplantation of pancreatic islets for the treatment of diabetes mellitus is widely anticipated to eventually provide a cure once a means for preventing rejection is found without reliance upon global immunosuppression. Long-term storage of islets is crucial for the organization of transplantation, islet banking, tissue matching, organ sharing, immuno-manipulation and multiple donor transplantation. Existing methods of cryopreservation involving freezing are known to be suboptimal providing only about 50% survival. The development of techniques for ice-free cryopreservation of mammalian tissues using both natural and synthetic ice blocking molecules, and the process of vitrification (formation of a glass as opposed to crystalline ice) has been a focus of research during recent years. These approaches have established in other tissues that vitrification can markedly improve survival by circumventing ice-induced injury. Here we review some of the underlying issues that impact the vitrification approach to islet cryopreservation and describe some initial studies to apply these new technologies to the long-term storage of pancreatic islets. These studies were designed to optimize both the pre-vitrification hypothermic exposure conditions using newly developed media and to compare new techniques for ice-free cryopreservation with conventional freezing protocols. Some practical constraints and feasible resolutions are discussed. Eventually the optimized techniques will be applied to clinical allografts and xenografts or genetically-modified islets designed to overcome immune responses in the diabetic host.     

Method of determining the colloidal status of the vitreous body

A new method for the quantitative estimation of the vitreous body colloidal state has been suggested. For realization of the method a fragment of the vitreous body and an equal volume of water are dried out, and the drying time is registered. The higher is the ratio between the drying time of the vitreous body fragment and water, the higher is the density of the vitreous body gel. The drying out of the vitreous body fragment and water on the analytical balance cups permits the registration of the drying out process in the time course. Thus some additional parameters are obtained that characterize the object studied more completely. The method can be used in experimental and clinical investigations of the vitreous body and other biological liquids.     

Flow and diffusion in the vitreous body of the eye

Solution of the equation that describes simulatenous liquid flow and diffusion in a spherical model of the vitreous body of the eye shows that a small dissolved specie can move both anteriorly and posteriorly from a source behind the lens even though there is a slow liquid movement almost entirely in the posterior direction. This results explains why tracer studies using large particles (dyes or colloids) show only a posterior flow, whereas studies using sodium ion show anterior movement as well.     

Comparative characteristics of the vitreous body proteins in vertebrates

Using disc-electrophoresis in polyacrylamide gel and immunochemical methods, studies have been made on proteins from the vitreous body of mammals (albino mouse, rat, guinea pig, pig, dog, cat), birds (hen), amphibians (the frog Rana ridibunda) and fish (the perch Perca fluviatilis). It was found that vitreous body proteins in man and animals include both the specific proteins and those of the blood serum. During evolution, specific antigens of the vitreous body attained strict species specificity, although some of them preserved the initial properties.