apyrase and Retinal-Artery-Occlusion

To quantify the acute constrictive response of developing retinal blood vessels to hyperoxia and to examine the vaso-obliterative phase of sustained oxygen breathing in the neonatal dog model of retinopathy of prematurity.. Seven littermates were used to examine the acute constrictive response of the developing retinal vessels to hyperoxia (30 minutes to 96 hours of 100% oxygen). ADPase retinal flatmounts were prepared, and morphometric measurements were made using computer-assisted analysis. Vaso-obliteration also was examined in three animals killed after prolonged exposure to hyperoxia (4 days of 100% oxygen) and in three room air controls using ADPase flat-embedded retinas and cross-sections. Choroids were processed for alkaline phosphatase flat-embedding.. After 1 hour of oxygen breathing, all vascular components showed a reduction in diameter: Arteries were reduced 27%, veins 18.3%, and capillaries 27.7%. Capillary constriction peaked by 24 hours (69.4% reduction), whereas arteries and veins continued to close. Although capillary diameters did not decrease significantly after 24 hours, the number of capillaries, as determined by percent vascular area calculations, continued to decrease in all areas through the additional 3 days of oxygen breathing. In contrast, after 4 days of hyperoxia the choriocapillaris lumenal diameters and percent vascular area did not vary significantly from controls. Analysis of sections taken through various retinal regions of these animals revealed significant decreases (40%) in the volume of the extracellular spaces available for blood vessel formation. Hyperoxia also reduced in a 55.6% decrease in the total number of cells (endothelial cells, ablumenal cells, perivascular cells) within the inner retina; however, there was no significant difference in ganglion cell counts in the two groups.. This study demonstrates that the pattern and severity of the reaction of developing retinal vessels to hyperoxia in the newborn dog is similar to that described for the kitten and the premature human. This response is unlike that exhibited by the newborn rat or mouse.

Topics: Animals; Apyrase; Cell Count; Choroid; Disease Models, Animal; Dogs; Humans; Hyperoxia; Infant, Newborn; Mice; Oxygen; Rats; Retinal Artery Occlusion; Retinal Vein Occlusion; Retinal Vessels; Retinopathy of Prematurity

To examine the sickle cell retina in dual perspective (vascular patterns en bloc and structure in serial sections) to gain new insights into sickle cell retinopathy.. We analyzed the retinas of two patients with sickle cell disease (a 54-year-old patient with hemoglobin SC, heterozygous for the S and C mutation in the beta chain of the globin gene, and a 20-month-old patient with sickle cell anemia [SS], homozygous for the S mutation) using the previously described adenosine diphosphatase flat-embedding technique.. The dual-perspective analysis afforded by our technique revealed that the primary site of occlusions was located at the precapillary level. An unusual neovascular formation, the hairpin loop, was observed in both patients' retinas and appeared to result from recanalization of the wall of an occluded vessel. Many autoinfarcted pre-retinal neovascular formations were observed in the older SC patient. Two patent preretinal formations were studied in detail and their evolution appeared to be influenced by mechanical factors. The vessels appeared to have been extruded from the retina, perhaps owing to hydrostatic pressure secondary to downstream occlusions. Small pigmented lesions consisting of retinal pigment epithelial cells ensheathing channels that resembled autoinfarcted vessels were found in the eye of the SC patient.. This study illustrates unusual morphological features of intraretinal and preretinal neovascularization and of chorioretinal lesions in sickle cell retinopathy and suggests alternative mechanisms for their formation.

Topics: Adult; Anemia, Sickle Cell; Apyrase; Choroid Diseases; Electron Probe Microanalysis; Female; Humans; Infant; Male; Middle Aged; Retinal Artery Occlusion; Retinal Diseases; Retinal Neovascularization; Retinal Vessels; Tissue Embedding