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No loss in the in vivo efficacy of ischemic preconditioning in middle-aged and old rabbits

^a Heart Institute, Good Samaritan Hospital and the Department of Medicine, Section of Cardiology, University of Southern California, Los Angeles, California, USA

View larger version (22K): [in a new window]   Figure 1 (A) Risk region, expressed as percent total left ventricular (LV) weight, for adult, middle-aged and old rabbits. Results of two-way analysis of variance: p = 0.79 for age; p = 0.94 for treatment; and p = 0.40 for age x treatment. (B) Necrosis, expressed as percent risk region, for adult, middle-aged and old rabbits. Results of two-way analysis of variance: p = 0.05 for age; p < 0.01 for treatment; and p = 0.90 for age x treatment. **p < 0.01 versus matched control group. Solid bars = control groups; open bars = PC groups.

View larger version (20K): [in a new window]   Figure 2 (A) Myocyte cross-sectional area (µm2) in adult, middle-aged and old rabbit hearts. Results of two-way analysis of variance: p < 0.01 for age; p = 0.75 for treatment; and p = 0.98 for age x treatment. (B) Percent collagen content in adult, middle-aged and old rabbit hearts. Results of two-way analysis of variance: p < 0.01 for age; p = 0.41 for treatment; and p = 0.97 for age x treatment. *p < 0.05 and p < 0.01 versus adult rabbits; p < 0.01 versus middle-aged rabbits. Solid bars = control groups; open bars = PC groups.

View larger version (89K): [in a new window]   Figure 3 Picrosirius red-stained sections from adult (A), middle-aged (B) and old (C) rabbit hearts, viewed with circularly polarized light, illustrating the age-related increase in myocardial collagen content. Thick collagen fibers appear yellow; thin fibers appear yellow-green; and myocytes are green and cross striated. Bar = 50 µm.

View larger version (23K): [in a new window]   Figure 4 Peak positive LV dP/dt (LV dP/dtmax; expressed as a percentage of baseline values) during isoproterenol infusion in adult, middle-aged and old rabbits. Results of two-way analysis of variance: p < 0.01 for age; p < 0.01 for dose; and p < 0.01 for age x dose. p < 0.01 versus adults; p < 0.01 versus baseline. Solid bars = adult rabbits; striped bars = middle-aged rabbits; open bars = old rabbits.