Muscle Fiber and Mitochondria (IMAGE) Cell Press Caption This is an electron micrograph of a muscle fiber and subpopulations of intermyofibrillar mitochondria (mt). Credit Leigh Thorne, M.D. Usage Restrictions Credit Required. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.