Figure 6.

Quantitative imaging of lipid droplet chemistry in muscle using hyperspectral CARS microscopy. One complete hyperspectral dataset contained spectral data from Type I and Type II muscle fibers in a human muscle biopsy of m. vastus lateralis. LDs were identified from the tissue based on image thresholding similar to [39] and additional data segmentation was performed to group LDs by fiber type. This allowed for producing LD specific spectra from each fiber type and from the non-LD area. Average spectra from LDs in Type I (red) and Type II (blue) fibers and the total non-LD area (green) highlight differences in chemical environment between the LDs between different fiber types and from LDs to the sarcoplasm. Images show chemical images of esters (C O) and CH₂ symmetric vibrations. LDs in type I fibers contain more esters, yet similar CH₂, compared with Type II fibers, which suggests a differential type of neutral lipid storage between fiber types in the same muscle. (Unpublished data, SD, MKCH, and SHP).