Transmission electron microscopy and point-counting of subcellular lipid droplets A, acquisition of electron micrographs was systematically randomized to cover the subsarcolemmal (SS), superficial myofibrillar (SMF) and central myofibrillar regions (CMF) of each longitudinally oriented fibre. The arrow indicates the sarcolemma. (original magnification ×600, scale bar: 20 µm). B, subcellular localisations of lipid droplets. The arrow indicates the sarcolemma. C, close-up view of point-counting of subsarcolemmal lipid droplet volume fraction with grid (size 135 nm) overlay. The open circles indicate intersections touching a lipid droplet. * , a subsarcolemmal lipid droplet; * * , an intermyofibrillar lipid droplet; Mi, mitochondria; Z, Z-line. (Original magnification ×10,000, scale bar: 1 µm.)

Transmission electron microscopy and point-counting of subcellular lipid droplets A, acquisition of electron micrographs was systematically randomized to cover the subsarcolemmal (SS), superficial myofibrillar (SMF) and central myofibrillar regions (CMF) of each longitudinally oriented fibre. The arrow indicates the sarcolemma. (original magnification ×600, scale bar: 20 µm). B, subcellular localisations of lipid droplets. The arrow indicates the sarcolemma. C, close-up view of point-counting of subsarcolemmal lipid droplet volume fraction with grid (size 135 nm) overlay. The open circles indicate intersections touching a lipid droplet. * , a subsarcolemmal lipid droplet; * * , an intermyofibrillar lipid droplet; Mi, mitochondria; Z, Z-line. (Original magnification ×10,000, scale bar: 1 µm.)

Contexts
Context 1
... make robust and unbiased volume estimates of lipid droplets and mitochondria (for fibre-typing, see below), we used point-counting techniques, with reference to Cavalieri's principle and the Delesse principle (Weibel, 1979), to estimate areas of mitochondria and lipid droplets in the electron micrographs (Fig. 1). Identification of mitochondria in micrographs was based on previously reported work on mammalian skeletal muscles (Hoppeler et al. 1973). Our criteria for identifying lipid droplets included having a circular white-greyish appearance with a fuzzy border (absence of distinct membrane) and a minimum diameter of 200 ...

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