Ultrastructural and immunocytochemical study of the leptomeres in the mouse cardiac muscle fibre

Abstract

The three-diiiiensional configuration and cheiriicol composition of leptoniei-es in the inouse \ e i i t r i c ~ i l a r cardiac inuscle fibre were electron iiiicroscopically und iminuiiocytochemically in\-estigated ~ising seinithin sections and specific antibodies agairist actin. the intei-mediate filament proteins desinin and viiiientin. anci the aciin-binding proteins a-actiriin, filainin and vinculin. The leptomeres appeared columnar in shape arid periodically segmeiited by electron-dense tiisc-like septa. The electrori-lucent areas betweeri these septa uere composed of fiiie interlinked filainents running obliquely to the major axis cif the Ieptomere. Actiii was localized in the electron-dense lii-ies of the leptoineres but not in the fine filaments. No reaction was. however. detected for desinin. vinientin. \zi~iculin. rilainin and a-actinin. The preserit results suggest. therefore. that the leptomeres inay not have a contractile function