ABSTRACT
Objective To investigate the medium and long-term influence of silicon oil versus heavy silicone oil on rabbit retinas.Methods 28 health standard rabbits were randomly divided into A,B and C groups,with 12,12 and 4 rabbits respectively.All rabbits received routine vitrectomy and tamponade with silicone oil (group A),or heavy silicone oil (group B) or balanced salt solution (group C).After 4,8,12 and 24 weeks,the retinal b-wave amplitude was measured by ERG,posterior retinal thickness was measured by optical coherence tomography (OCT).Retinal ultrastructure and tissue morphology were observed by transmission electron microscopy and optical microscopy.Results Compare to group C,the b-wave amplitude decreased at 4 weeks after surgery,and decreased at 8 weeks after surgery for group B,and decreased at 8 weeks after surgery,and decreased at 24 weeks after surgery for group A.The decreases were greater in group B than group A at 8,12,24 weeks after surgery,the difference was statistically significant (P＜0.05).The posterior retinal thickness of group A and B was thinner than group C at 24 weeks after surgery (P＜0.05).The decreases were greater in group B than group A,the difference was statistically significant (P＜0.05).Transmission electron microscopy and optical microscopy revealed severe pathological changes of retinal ultrastructure and morphology in group A and B rabbit eyes,at 12 weeks and 8 weeks after surgery respectively.The changes were more severe in group B and group A,including edema and necrosis in cone/rod cells,in disk membranes,mitochondria,cytoplasm,nucleus and other organelles.The morphological changes were also more severe in group B and group A,including degenerations of ganglion cell layer,inner nuclear layer changes.Those changes became more severe when the tamponade time extended.Conclusion The heavy silicone influence on visual function,ultrastructures,histomorphology of rabbit retinas is much worse than the silicon oil,and the effect is more significant with its time prolong.
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Objective To study on the ultrastructural characteristic of segments of photoreceptors from neonatal retinas for supporting donor retina choice of retinal transplantation. Methods Photoreceptors from neonatal calf and adult calf were analysed by scanning electron microscopy and transmission electron microscopy. Results Segments of photoreceptors from neonatal calf appeared the mushroom pattern, in which, distal end of outer segment which was ball shaped formed the head with mushrooms appea rance, and the inner segments along with some of outer segments formed the body with mushrooms appea rance. Within the outer segment, plasma membranes of adjacent evaginations form a disk subsequently. The array of most disks were vertical to the entire length of segments, but some were parallel and slope to. Owing to the incomplete formation, some rim of disk near distal end of outer segment revealed step shaped appearance. The distal end of outer segment displays some processes consisted of membranous discs, much vesicular material and mitochondria, much rough endoplasmic reticulum (RER) and numerous polysomes. Segments of photoreceptor connected with outer nuclear layer via the external limiting membrane. Conclusion The typical morphological structures of outer segments suggest the immature and strong gowth ability of photoreceptors of the retina of neonatal calf, and therefore the competence for donor material of retinal transplantation.
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Objective To observe the ultrastructural characteristics of human retinal progenitor cells cultured in vitro. Methods Six 5-month-old human fetuses(12 eyes)without eye diseases were selected. Retinal progenitor cells from the retina of one eye of each fetus were cultured in vitro,and observed by transmission electronic microscopy(TEM); while those from the other eye were directly observed by TEM. Results Abundant heterochromatin were found in the karyon of 5-month embryonic retinal neuroepithelial cells,and the figure of the karyons was irregular.A few scattered initial cells were seen in retinal neuroepithelial layer with large karyon,smooth surface,abundant euchromatin,and distinct nucleolus.The human retinal progenitor cells cultured in vitro had the same ultrastructural characteristics as the initial cells:with huge karyon which almost occupied the whole cell,little cytoplasm,distint nucleolus,abundant euchromatin,and little heterochromatin.The cells clung to each other in the neural globoid cell mass.The size of the outer cells was large,and karyokinesis could be found. Conclusion The cultured human retinal progenitor cells are provided with the same ultrastructure characteristics as the initial cells.