Analysis of fibrous proteins from electron microscopy images

Fine structure of extracellular fibers in primo-nodes and vessels

To investigate the extracellular matrices in the primo-nodes (PNs) and vessels (PVs) (Bonghan corpuscles and ducts), fine structure of the fibers comprising the extracellular matrices was studied in relation to the diameter and the periodicity to identify the types of the fibers. Electron micrographs of the fibers from the previously published works on the PNs and PVs were analyzed by using MATLAB programming and ImageJ software. The extracellular fibrous components of the PNs and PVs could be classified generally into two groups--thin collagen fibrils and thick non-collagenous wavy bent fibers. The thick bent fibers were fibrin-like. The diameters of the thick bent fibers were 30-200 nm and they were highly bent. This group included organ surface PNs and lymphatic PNs/PVs. The diameters of the collagen fibrils were 30-70 nm. Organ surface, heart, and hypodermis PVs were categorized in this group. The periodicity of bent fibers in an organ surface PN was 16.1 +/- 0.2 (SE) nm, and the periodicity of collagen fibrils in the hypodermis PVs was 37.4 +/- 0.5 (SE) nm. Further investigations are required to reveal the physiological implications of the two types of fibers in the PNs and PVs.

Viscoelastic and failure properties of spine ligament collagen fascicles

The microstructural volume fractions, orientations, and interactions among components vary widely for different ligament types. If these variations are understood, however, it is conceivable to develop a general ligament model that is based on microstructural properties. This paper presents a part of a much larger effort needed to develop such a model. Viscoelastic and failure properties of porcine posterior longitudinal ligament (PLL) collagen fascicles were determined. A series of subfailure and failure tests were performed at fast and slow strain rates on isolated collagen fascicles from porcine lumbar spine PLLs. A finite strain quasi-linear viscoelastic model was used to fit the fascicle experimental data. There was a significant strain rate effect in fascicle failure strain (P < 0.05), but not in failure force or failure stress. The corresponding average fast-rate and slow-rate failure strains were 0.098 ± 0.062 and 0.209 ± 0.081. The average failure force for combined fast and slow rates was 2.25 ± 1.17 N. The viscoelastic and failure properties in this paper were used to develop a microstructural ligament failure model that will be published in a subsequent paper.

The role of collagen in bone structure: An image processing approach

Bone collagen structure in normal and pathological tissues is illustrated using techniques of thin section transmission electron microscopy and computer-assisted analysis. The normal bone collagen types, fibril architecture and diameter are described. In pathological tissue, deviations from normal fine structure are reflected in abnormal arrangements of collagen fibrils and abnormalities in fibril diameter. Computer analyses of normal fibril positive staining patterns are presented in order to provide a basis for comparing such patterns with pathological ones.