Non-collagenous Material Research Articles

Variation of chemical composition with age in human femoral head cartilage.

The chemical composition of intact femoral head cartilage was investigated with age. Full-depth cartilage showed a decrease in water content and an increase in keratan sulphate and noncollagenous material with age. When analyzed through the depth of the cartilage, keratan sulphate was shown to appear first in the deep zones and later in the surface, while water content was lost mainly in the deep zones. On a dry weight basis collagen content decreased with age. This was not a real loss but was due to a change in the proportions of other materials, mainly in the deep zones.

Production of procollagen by human fibroblasts in culture.

Three hydroxyproline-containing proteins secreted into the medium by human fibroblasts in culture were isolated and characterized. A minor fraction was identical to the collagen monomer. The major fraction was a form of procollagen, which contained, in addition to pro alpha and alpha chains, a component estimated to have a molecular weight of 250,000. This component was a dimer of pro alpha chains joined by disulfide bonds. The third fraction, much lower in hydroxyproline and hydroxylysine content, was of still greater size. Pro alpha chains were released upon denaturation and reduction, indicating that this fraction may contain pro alpha chains linked by disulfide bonds to noncollagenous material.

The distribution of hydroxyproline in the dentine of carious human teeth

Loss of hydroxyproline from dentine matrix was used as a means of correlating the pattern of attack in the collagenous matrix due to caries, with the pattern of demineralization as shown by microradiography. Samples of dentine, 150 μm in diameter, were removed from undecalcified sections of carious teeth, along lines passing through the lesion and through adjacent sound dentine. The hydroxyproline content of the samples was estimated using a method working in the range 0–80 ng and the results expressed as μg/mm 3 of dentine. This basis of expression gave results unaffected by density variations or contamination of the carious dentine by foreign, non-collagenous material. Results indicated an increased collagen content in sclerotic dentine beneath the lesion and at the demineralization front, compared with corresponding sound dentine, falling towards the surface of the lesion, where a concentration of intact collagen lower than that found in corresponding normal dentine was indicated. The results suggest that the organic matrices of peritubular dentine and intratubular deposits in sclerosed tubules are collagenous.

Calcificationin vitro of demineralized bone matrix

Collagen was prepared from compact sheep bone by decalcification with EDTA and from rat tail tendons by acetic acid extraction and reconstitution with NaCl. The deposition of apatite in sheep bone collagen in a metastable calcification solution was studied chemically and by electron microscopy. The bone collagen was shown to be a good nucleation catalyst for mineral deposition, while rat tail collagen was a poor catalyst. Mineral deposition in bone collagen occured in two separate kinetic phases, a rapid phase of nucleation and crystal growth, giving rise to small calcified islands, and a second slow phase, ascribed to growth in regions not involving the catalytic sites. This second phase of mineral deposition is considered to be the result of impaired ion diffusion through the closely-aligned collagen fibrils, thus leaving large areas of the collagen free of mineral even though the buffer remains highly supersaturated. Electron micrographs suggested that the catalytic sites might be in some relationship to the 640 A periodicity of collagen, but a role for non-collagenous material bound to the collagen has not been excluded.

Fractionation of pepsin-digested, denatured collagen: III. Characterization of the small fragments

The survey 1,2 of the fragments obtained from pepsin-digested, denatured rat tail tendon collagen is completed. Three additional fragments could be renatured and two of them (490 Å and 670 Å) were located in tropocollagen by electron microscopy. Data are given on the amino acid compositions of the various fractions. Certain fragments probably originated from the associated non-collagenous material belonging to the “acidic structural proteins”.

Wound healing and collagen formation. III. A quantitative radioautographic study of the utilization of proline-H3 in wounds from normal and scorbutic guinea pigs.

The sequence of incorporation and utilization of tritium-labeled proline has been examined in healing wounds from normal and scorbutic guinea pigs. Linear incisions in the skin of the animals were allowed to heal for 7 days. Each animal was given proline-H(3), and the wounds were excised 30 minutes, 1 and 4 hours, 1, 3 and 7 days after proline administration. The tissues were fixed in osmium tetroxide, fixed again in neutral buffered formalin, embedded in epoxy resin, and sectioned at 1 micron thickness. The sections were coated with nuclear track emulsion, exposed, developed, and stained. The results of grain counts were quantitated as the number of counts per unit area overlying cells, fibers, etc. In both groups the proline reaches a maximum over the fibroblasts within 4 hours and subsequently disappears from the cells. Concomitantly, the proline reaches a maximum over the collagen (in normal animals) and extracellular fibrillar material (in scorbutic animals) by 4 hours, where it remains. The modified technique of radioautography used in this study allows not only resolution of approximately 1 micron, but also minimal background, decreased artifact, and a clear separation of the randomly situated elements within the wounds so that grain counting is facilitated. The results correlated with previous electron microscopic studies are consistent with the utilization of proline by the fibroblasts and its incorporation into collagen (in normal animals) and into the extracellular, fibrillar, non-collagenous material seen in scorbutic animals.