Collagen fibres

Random collagen fibres provide an insoluble gel-like primary network and polyanionic hyaluronic acid a secondary network, which confers the viscoelastic property and stabilizes the collagen network (Balzas and Delinger, 1984). 

The individual collagen ropes are called fibrils, and have an average molecular weight of around 300 000 Daltons (atomic mass units), with a length of 260 nm and a diameter of 1.4-2.0 nm. In the collagen fibres which can be seen... 

The various cell types are distributed differently within various types of connective tissue fibroblasts often found lying close to collagen fibres, whilst macrophages and mast cells usually appear in clusters around blood vessels. Additionally, whereas fibroblasts are widespread, macrophages are absent from some types of connective tissue, tendons for example. Specialized cells also occur within particular locations for example osteoblasts and osteoclasts (bone), chondrocytes (cartilage), adipocytes (fat tissue) and haemopoietic cells (bone marrow). 

Feverfew extract was shown to inhibit deposition, aggregate formation and spreading of platelets on collagen fibres [54]. Changes in membrane-cytoskeletal interaction leading to a change in expression of membrane receptors involved in these processes may explain this result. Feverfew extract was further able to protect the endothelial monolayer in rabbit aortas from perfusion injury and some reversible increase in cAMP levels in the aorta segments was found [55]. 

Robins SP and Bailey AJ (1977) Some observations on the ageing in vitro of reprecipitated collagen fibres. Biochim Biophys Acta 492, 408-414. 

With an approximate volume of 4 ml, the vitreous is the largest structure within the eye. It has a refractive index of 1.33 and consists of 98-99% water with a scaffold of collagen fibres and macromolecules of hyaluronic acid winding through the scaffold. The healthy human vitreous does not contain blood vessels and has a consistency comparable to that of egg white. 

Interest in the role of the matrix in mineralization was reawakened by the demonstration, that the crystals in bone were highly oriented with respect to the collagen fibres. This in turn has led to studies on the chemical nature of the matrix related to its ability to calcify184). 

In the second stage, as the needle-like calcium phosphate deposits radially grow out of the vesicles, the surrounding collagen fibres become mineralized. 

From the assumption that the collagen fibres are expanded, it also follows that the diameter values of calcium phosphate nuclei should exceed the value of 16 A, which is the minimum diameter of the microchannels (i. e. the diameter when the subfibrils are in direct contact). 

Histological data have shown an early fibroblast reaction, formation of collagen fibres and differentiation of connective tissue on treatment of wounds with silatranes6... 

As you can see in the figure above, bone is porous. This porosity appears to increase its strength, consequently without porosity bones would not only be heavier, but they would also break more easily. Figure 12.2. illustrates how the collagen fibres and crystals are joined together to form larger units and finally bone. 

Collagen fibres (a) and hydroxyl apatite crystals (b) together form larger units, the so-called micro-fibrils (c). It should be pointed out here that the collagen fibres are helically intertwined and consequently... 

Mrevlishvili189 gave the following enthalpy differences for the helix-coil transfer of collagen fibre - coils/solution (5 kcal/mole) coils/solution - helix/solution (—5.5 kcal/mole) helix/solution - helix/fibre (0.5 kcal/mole). The following table gives the differences between the hydration water of native and denaturated protein181,188> ... 

Hulmes, D. J. S., Miller, A., White, S. W., and Brodsky-Doyle, B. (1977). Interpretation of the meridional diffraction pattern from collagen fibres in terms of the known amino acid sequence. / Mol. Biol. 110, 643-666. 

Oguma, H., Murakami, G., Takahashi-Iwanaga, H., Aoki, M., and Ishii, S. (2001). Early anchoring collagen fibres at the bone-tendon interface are conducted by woven bone formation. /. Orthopaedic Research 19, 873-880. 

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