Structural Chemistry of Outer Dense Fibers of Rat Sperm1

Abstract

Rat sperm outer dense fibers (ODF) have been studied by several electron microscopic techniques to determine fine structural features of the ODF cortex and medulla. Cross sections of Triton X-100 demembranated flagella, fixed in the presence of ruthenium red, reveal a well defined ODF cortex which appears to be composed of a single lamina of 6-7 nm diameter globular particles, whereas the medulla appears electron dense with no obvious substructure. Surface replicas and positively or negatively stained whole mount preparations reveal a crossbanding pattern with a 40 nm major period repeat that extends obliquely over the outer dense fiber surface. These periodicities appear to be confined to the outer dense fiber cortex.