SCANNING-TRANSMISSION ELECTRON-MICROSCOPY MASS ANALYSIS OF FIBRILLIN-CONTAINING MICROFIBRILS FROM FETAL ELASTIC TISSUES

We have applied scanning transmission electron microscopy to intact na tive fibrillin-containing microfibrils isolated from foetal bovine ela stic tissues in order to derive new insights into microfibril organisa tion. This technique provides quantitative data on the mass per unit l ength and axial mass distribution of unstained, unshadowed macromolecu les. Scanning transmission electron microscopy of microfibrils from ao rta, skin and nuchal ligament revealed that the beads corresponded to peaks of mass and the interbead regions to troughs of mass. These majo r features of axial mass distribution were characteristic of all micro fibrils examined. Tissue-specific and age-dependent variations in mass were identified in microfibrils that were structurally comparable by rotary shadowing electron microscopy. Increased microfibril mass corre lated with increasing gestational age. The additional mass was associa ted predominantly at, or close to, the bead. Some microfibril populati ons exhibited pronounced assymetry in their axial mass distribution. T hese data indicate that intact native microfibrillar assemblies from d eveloping elastic tissues are heterogeneous in composition. Loss of ma ss following chondroitinase ABC or AC lyase treatment confirmed the pr esence of chondroitin sulphate in nuchal ligament microfibrillar assem blies. (C) 1997 Published by Elsevier Science Ltd.