Elastin-associated microfibrils in aorta: species differences in large animals

Abstract

As part of a comparative study of elastic tissue morphology, we have adapted a method for measuring accurately, in tissue sections, differences in the diameters of the microfibrils associated with aortic elastic tissue. The method is reproducible to within ± 2%. Measurements have been made of the diameters of microfibrils associated with the internal elastic lamellae of the thoracic descending aortae of members of four species of large animals commonly used in the study of elastic tissue. Healthy mature young adult male animals have been examined so as to avoid differences associated with development and disease. Rigorous attention has been given to standardisation of fixation, processing, microscopy and measurement. A single negatively stained catalase crystal was used as reference standard for the calibration of each series of electronmicrographics. It has been found that sheep and bovine aortic microfibrils are not significantly different in diameter. However, their mean diameters are significantly and reproducibly different from those of humans and pigs (in order of increasing diameter). The mean diameters of the microfibrils of the latter two species are also significantly different from one another. Comparison of the catalase crystal with tobacco mosaic virus and with other catalase preparations revealed highly significant and reproducible differences in the crystal lattice spacing of different catalase preparations available commercially.