Multilamellar bodies as potential scattering particles in humanage-related nuclear cataracts

[摘要] Purpose: To characterize within human age-related nuclear cataractsrare spherical objects covered by multiple membranes, termedmultilamellar bodies (MLBs).Methods: Adult human normal, transparent lenses were obtained fromeye bank donors and age-related nuclear cataracts were obtainedimmediately after extracapsular extraction. Each sample was Vibratomesectioned fresh into 200 mm thick sections that were fixed andembedded for light or electron microscopy. Confocal images were recordedfrom sections stained with the lipid soluble dye, DiI.Results: Light micrograph montages of the equatorial planecontaining the fetal and embryonic nuclei were examined. Rare, butdistinct, circular 1-3 mm diameter objects were observed consistentlyin the cataracts. These objects did not appear to be components of thecomplex intercellular interfaces. Serial sections indicated that theobjects were spherical, or contained a spherical component. For about20,000 fiber cell cross-sections in each lens, the frequency of MLBs was10 times higher in cataracts than in the normal lens nuclei. Althoughextensive searching with the electron microscope was necessary, thesize, circular profile and multiple layers of thin (5 nm) membraneseasily identified the MLBs. Interiors of the MLBs displayed variabletextures. Confocal images indicated that the coverings were enriched inlipid compared to the adjacent plasma membranes. The calculated densityof the MLBs in the cataractous nuclei was about 3800/mm3, whichrepresents a volume fraction of 0.00003.Conclusions: Because the MLBs are large compared to the wavelengthof light, display interiors with variable staining textures and havelipid-rich coverings, they appear to be ideal candidates for largescattering particles that may contribute to the forward light scatteringin nuclear cataracts.

[学科分类] 生物化学/生物物理