Wool-fibre Crimp Part I: The Effects of Microfibrillar Geometry

The three-dimensional arrangement of intermediate filaments in Romney wool cortical cells

“…Furthermore, this short-range evidence suggests that each IF is restricted to a righthanded helical path of approximately constant radius. Long-range data are needed to confirm whether the orthocortical IFs are helically wrapped or twisted as, for example, the fibres in a yarn (Munro and Carnaby, 1999).…”

“…Electron diffraction studies by Dobb (1970) and compositional studies by Campbell et al (1975) also support these conclusions. It has been proposed by Dobozy (1959), Brown and Onions (1961) and, more recently, Munro and Carnaby (1999) that the bilateral arrangement of orthocortical and paracortical cells of high crimp, fine wool fibres creates a differential strain in the longitudinal extension properties of the fibre. When going from the wet to dry state, the fibre undergoes lateral contraction with a corresponding longitudinal extension on the orthocortical side due to the greater inclination of the IFs.…”

Cortical cell types and intermediate filament arrangements correlate with fiber curvature in Japanese human hair

“…Highcurvature fine wool has a bilateral cortical cell distribution with orthocortical cells containing helically arranged IFs located mainly in the convex fiber half, and paracortical cells containing pseudohexagonally packed, parallel arrays of IFs located in the concave fiber half (Kaplin and Whiteley, 1978;Orwin et al, 1984). Single fiber curvature theory (Dobozy, 1959;Brown and Onions, 1961;Munro and Carnaby, 1999) assumes that as the moisture-saturated wool fiber is extruded from the follicle, the fiber dries, and the matrix protein material located between the water-impervious IFs shrinks laterally. In Mfs with helical IF regions, lateral contraction causes a small decrease in IF helical tilt and a corresponding longitudinal extension of the Mf, but in Mfs with IFs aligned in parallel, such a mechanism is absent and extension is negligible.…”

“…Matrix staining variability and IF arrangements are useful identifiers of cortical cell types (Horio and Kondo, 1953;Rogers, 1959a;Bonés and Sikorski, 1967;Kaplin and Whiteley, 1978;Orwin and Bailey, 1988). Fiber curvature has been hypothesized to result from the interaction between different 3D IF arrangements (inferred from 2D TEM images) and the matrix material following dehydration as the fiber emerges from the follicle (Munro and Carnaby, 1999;Munro, 2001). Electron tomography directly confirmed the different IF arrangements in wool cortical cell types (Bryson et al, 2000;Caldwell et al, 2005a,b), enabling further mathematical modeling and computer assimilations to test hypotheses predicting the effect of IF arrangements on single fiber curvature (Bryson et al, 2001;Bryson, 2002, 2005).…”

Application of proteomics for determining protein markers for wool quality traits

“…High magnification electron microscopical images of cortical transverse sections reveal well-ordered geometric arrangements of intermediate filaments (IF), also known as microfibrils, which differ with each cell type [4,5]. A computational, predictive model describes how the geometrical arrangements of IF could effect crimp frequency [6] but this still needs experimental verification. However, powerful experimental data exists from recent immunolocalisation studies and work with cRNA probes [7,8] in hair follicles and has shown that genes encoding the high glycine tyrosine proteins (HGTPs) are activated in cells of the orthocortex and soon after those encoding the high sulphur proteins (HSPs) are activated in the other half, the paracortex.…”