The Fine Structure of Lipofuscin Age Pigment in the Nervous System of Aged Mice

An examination of the topographic distribution of lipofuscin pigment granules with the light and electron microscope revealed either smaller and randomly "dispersed" or larger and more complex "clustered" pigment configurations in the cytoplasm of neurons in the dorsal ganglia and ventral spinal cord of 24-month old male mice. Qualitative comparisons revealed no major differences in shape, size, complexity, density, orientation, and cytologic distribution of the pigment bodies in motor and sensory neurons. In general, when the pigment granules were quite numerous within the 2 types of cells, they were smaller in size ( approximately lmicro), had a dense homogeneous matrix with few bands or lamellae, and were uniformly distributed throughout the cytoplasm. In contrast, when the pigment configurations were less in number, they were usually larger in size ( approximately 3micro), had a more complex internal banded structure, and appeared more localized within the cell. Examination of the bands revealed a repeating pattern of approximately 70 A. The bands appeared to fuse, forming hexagonal arrays of linear densities intersecting at an angle of approximately 120 degrees in some regions of the pigment bodies. Structural similarities suggested that the striated membranous bands may be composed of phospholipids.