No abstract

The mechanisms for retention of SS red cells in retina and choroid appear identical: hypoxia-mediated retention of dense red cells and adherence of red cells in reticulocyte-rich fractions after cytokine stimulation. TNF-alpha-stimulated retention of SS red cells in choroid appears to be mediated by VLA-4, presumably on the surface of some reticulocytes. This increased retention was inhibited by a VLA-4 antagonist (TBC772), a VLA-4 neutralizing antibody or by blocking one of VLA-4's ligands, the CS-1 portion of fibronectin.

* BACKGROUND AND OBJECTIVE: To study the heat and power dissipation effect of an intraocular electronic heater on the retina. The determination of thermal parameters that are nonharmful to the retina will aid in the development of an implantable intraocular electronic retinal prosthesis. * MATERIALS AND METHODS: In dogs, five different retinal areas were touched with a custom intraocular heater probe (1.4 × 1.4 × 1.0 mm) for 1 second while the heater dissipated 0 (control), 10, 20, 50, or 100 mW. In a second protocol, the heater was mechanically held in the vitreous cavity while dissipating 500 m W for 2 hours while monitoring intraocular temperature. The animals were observed for 4 weeks with serial fundus photography and electroretinography. The procedure was then repeated in the fellow eye. The dogs were killed and both eyes were enucleated and submitted for histology. * RESULTS: In experiments using protocol 1, heater settings of 50 mW or higher caused an immediate visible whitening of the retinal tissue. Histologically, this damage was evident only if the eyes were immediately enucleated. Permanent damage was caused by heater settings of 100 m W or higher. Under protocol 2, no ophthalmologic, electroretinography, or histologic differences were noted between the groups. Temperature increases of 5°C in the vitreous and 2°C near the retina were noted. * CONCLUSIONS: The liquid environment of the eye acts as a heat sink that is capable of dissipating a significant amount of power. An electronic chip positioned away from the retina can run at considerably higher powers than a chip positioned on the retinal surface. [Ophthalmic Surg Lasers Imaging 2003;34:114-120.]