Fig. 3.

Decreased mitochondrial volume and respiratory function in muscle of Clock^Δ19 and Bmal1^−/− mice. (A) Low-magnification EM images (4,000×) of skeletal muscle from wild-type, Clock^Δ19, and Bmal1^−/− mice. The white arrow in each image points to the region of the muscle under the sarcolemma where there are abundant mitochondria (wild type) or where mitochondria are lacking (Clock^Δ19 and Bmal1^−/−). (B) Histogram of mitochondrial volume measured using point-counting morphometry. The values are presented as a percentage of muscle-fiber volume from wild-type (black bar), Clock^Δ19 (gray bar), and Bmal1^−/− (open bar) mice. Values represent mean ± SEM (n = 5 muscles/strain) with significance (P < 0.05) denoted by an asterisk. (C) Representative high-magnification EM images (21,000×) of mitochondria within skeletal muscle of wild-type, Clock^Δ19, and Bmal1^−/− mice. Note swollen size and disrupted cristae of the mitochondria from muscle of Clock^Δ19 and Bmal1^−/− mice. (D) Histograms of biochemical measurements of respiratory control ratio (RCR) in gastrocnemius (GTN) and diaphragm (DIA) muscles of wild-type and Bmal1^−/− mice (n = 6/strain). Values are means ± SEM with significance (P < 0.05) denoted by an asterisk. (E) Histograms showing significant reduction in state III respiration (ADP-stimulated, mmol O₂/min/mg protein) in mitochondria isolated from GTN muscle of Bmal1^−/− mice compared with wild type. Values are means ± SEM with significance (P < 0.05) indicated by an asterisk.