Purpose. To employ Mie scattering theory to predict the light-scattering from micrometer-sized particles surrounded by lipid shells, called multilamellar bodies (MLBs), reported in human age-related nuclear cataracts.

A brief summary of current cryo–electron microscopy methods for processing and imaging biological tissues is provided. The main emphasis is given to two preparation procedures: frozen-hydrated samples because of the remarkable success of cryo-electron crystallography in obtaining near atomic resolution of integral membrane proteins, and high-pressure freezing because of the wide applicability for vitrification of large samples of normal and diseased tissues for ultrastructural and immunolabeling analysis. Methods for examining certain samples with a TEM cryo-stage are summarized. This includes an introduction to the relatively new area of cryo-electron tomography, which offers the possibility to observe the three-dimensional structure of subcellular components using only their natural variations in composition to generate contrast.

Recent evidence points to autophagy as an essential cellular requirement for achieving the mature structure, homeostasis, and transparency of the lens. Collective evidence from multiple laboratories using chick, mouse, primate, and human model systems provides evidence that classic autophagy structures, ranging from double-membrane autophagosomes to single-membrane autolysosomes, are found throughout the lens in both undifferentiated lens epithelial cells and maturing lens fiber cells. Recently, key autophagy signaling pathways have been identified to initiate critical steps in the lens differentiation program, including the elimination of organelles to form the core lens organelle-free zone. Other recent studies using ex vivo lens culture demonstrate that the low oxygen environment of the lens drives HIF1a-induced autophagy via upregulation of essential mitophagy components to direct the specific elimination of the mitochondria, endoplasmic reticulum, and Golgi apparatus during lens fiber cell differentiation. Pioneering studies on the structural requirements for the elimination of nuclei during lens differentiation reveal the presence of an entirely novel structure associated with degrading lens nuclei termed the nuclear excisosome. Considerable evidence also indicates that autophagy is a requirement for lens homeostasis, differentiation, and transparency, since the mutation of key autophagy proteins results in human cataract formation.