Assessment of axial bone rigidity in rats with metabolic diseases using CT-based structural rigidity analysis

Several patients with Fabry's, Gaucher's diseases and hyperlipoproteinemia type II and with arthropatic manifestations were observed.As no histological explanation for these symptoms was available,an ultrastructural study of synovial tissue was done to establish an anatomoclinical relation.Material and Methods :synovial membrane samples were obtained by needle biopsies of the knee from three patients with arthropatic manifestations of each disease.They were fixed in 5% glutaraldehyde, postfixed in 1% osmium tetraoxyde and embedded in Epon 812. Thin sections coloured by uranyl acetate and lead citrate were observed with an Elmiskop I Siemens electron microscope.Two important phenomena were observed in synovial tissue:Specific patterns of each lipid storage disease,which are now well known.In all the three metabolic diseases, hydroxyapatite-like crystals were found. They are characterized by their intramitochondrial localization, without any relation with cristae,an anarchic disposition and a mean size of 550 A.Crystals may be found also free in the cytoplasm of synoviocytes Some micrographs suggest an evolution in four steps :a. mitochondria with only a few microcrystalsb. mitochondria stuffed with these structuresc. disruption of mitochondria membranesd. microcrystals appear free in the cytoplasm

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The Organization of Actin Filaments in the Stereocilia of the Bird Cochlea

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600002452 ◽

1980 ◽

Vol 38 ◽

pp. 554-555

Author(s):

E.J. Battles ◽

D. DeRosier ◽

J.C. Saunders ◽

L.G. Tilney

Keyword(s):

Hair Cell ◽

Diffraction Pattern ◽

Sea Urchin ◽

Actin Filaments ◽

Optical Diffraction ◽

Dense Material ◽

Apical Surface ◽

Structural Rigidity ◽

High Degree ◽

Degree Of Order

Extending from the apical surface of each hair cell of the chick cochlea are from 75 to 200 microvilli or stereocllia and one true cllium, the kinocilium. The stereocllia are arranged in rows of progressively increasing length (Fig. 1). Within each tapering sterocilium is a bundle of actin filaments with over 900 filaments near the tip yet only approximately 25 at the base where filaments are enmeshed in a dense material (Fig. 1); from here some of the filaments enter the apical surface of the cell (cuticular plate) as a rootlet. Examination of longitudinal sections of the stereocilia (Fig. 2) show that the filaments are aligned parallel to each other and show considerable order. Examination of an optical diffraction pattern of this bundle (Fig. 4) reveal that the actin filaments are packed such that the crossover points of adjacent actin filaments are inregister. A prominent reflection at 125Å−1 demonstrates that the filaments are cjossbridged by a macromolecular bridge situated at an average of 125Å−1 intervals (Fig. 4) in transverse sections the filaments appear hexagonally packed although there are regions where the filaments are less ordered (Fig. 3). In images processed in the computer to remove, noise and enhance detail periodic nature of the bridge can be clearly seen (see arrows Fig. 5). This image resembles that of an actin paracrystal formed from sea urchin extract composed of bundles of actin filaments crossbridged by a second protein. Thus the actin filaments in the bird stereocilia by being cross-bridged and packed with a high degree of order and produces a structure with considerable structural rigidity. Embryos were studied at various stages in development in an attempt to determine how the stereocilia form and how does the actin packing develops. These stages will be discussed.

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