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Field emission scanning electron microscopic study on the noninfarcted myocardium after myocardial infarction
S Yano1, H Yoshikane, H Kawamoto
14th Department of Internal Medicine, Shimane Medical University, Izumo, Japan.
Abstract:
Intracellular membranous ultrastructural changes in the noninfarcted myocardium of the left ventricle were studied by examining experimental myocardial infarction in rats with a field emission scanning electron microscope. The left coronary artery was ligated at its origin for 7 days. The resulting infarcts comprised approximately 40% of the total area of the left ventricles. In a light microscopic study, the transverse diameter of myocytes had increased to 17.1 +/- 2.9 microns in the noninfarcted myocardium, compared to 14.1 +/- 3.1 microns in the myocardium of sham-operated rats (p less than 0.01). For the scanning electron microscopic study, the specimens were processed according to the Osmium-DMSO-Osmium method. Marked morphological changes of intracellular membranous structures were found in the noninfarcted myocardium, especially in the lacelike network of sarcoplasmic reticulum which occasionally formed large flattened cisternae, and in the marked proliferation of surface caveolae. It is speculated that these early ultrastructural changes in the noninfarcted myocardium reflect an adaptation of microorganellae in the failing hearts of the rats.
Insights
Experimental myocardial infarction in rats induced early ultrastructural changes in noninfarcted heart muscle. These adaptations in sarcoplasmic reticulum and caveolae may reflect a failing heart
Area of Science:
- Cardiovascular Biology
- Cellular Ultrastructure
- Experimental Pathology
Background:
- Myocardial infarction (MI) leads to significant cardiac remodeling.
- Understanding early cellular changes in noninfarcted areas is crucial for therapeutic development.
- Adaptations in cardiomyocyte ultrastructure may precede functional decline.
Purpose of the Study:
- To investigate intracellular membranous ultrastructural changes in the noninfarcted myocardium following experimental myocardial infarction.
- To characterize morphological alterations in cardiomyocyte organelles using advanced microscopy.
- To explore potential adaptive mechanisms in the failing heart.
Main Methods:
- Induction of experimental myocardial infarction in rats by ligating the left coronary artery for 7 days.
- Assessment of myocyte diameter using light microscopy.
- Detailed examination of intracellular structures using field emission scanning electron microscopy with the Osmium-DMSO-Osmium method.
Main Results:
- Infarcts occupied approximately 40% of the left ventricle area.
- Myocytes in the noninfarcted myocardium showed a significant increase in transverse diameter (17.1 ± 2.9 µm) compared to controls (14.1 ± 3.1 µm).
- Scanning electron microscopy revealed marked changes in sarcoplasmic reticulum, including flattened cisternae, and a proliferation of surface caveolae.
Conclusions:
- Early, significant ultrastructural modifications occur in the noninfarcted myocardium post-MI.
- Observed changes in sarcoplasmic reticulum and caveolae suggest adaptive responses within cardiomyocytes.
- These findings provide insights into the cellular mechanisms of cardiac adaptation in heart failure.