Collagen and related research最新文献

Avian type VI collagen is composed of three subunits of M_r 140,000, 150,000 and260,000. Monoclonal antibodies were raised against type VI collagen isolated from chick embryo gizzard, and these antibodies were used to immunoprecipitate type VI collagen from metabolically labeled embryo cells. Several antibodies appeared to react with epitopes independent of glycosylation and hydroxylation processes. The antibody-binding sites were identified on the different chains by immunoblotting of total cell extracts. In addition, antibodies that recognized different epitopes on the M_r 260,000 subunit could be grouped in at least three different clusters by competitive inhibition radioimmunobinding assays.

The organisation of collagen fibrils within the cervices from non-pregnant humansand rats and day 22 pregnant rats was measured using X-ray diffraction. This technique yields the direction of preferred orientation of the collagen fibrils and an orientation distribution function. In the human cervix there are three distinct zones which blend smoothly into each other on passing radially outward from the canal. Adjacent to the canal and in the outermost zone the fibrils are oriented predominantly longitudinally, that is parallel to the canal. In the middle zone the fibrils have a preferred orientation in a circumferential direction. A similar structure is seen in the non-pregnant rat cervix. The collagen fibrils in the day 22 pregnant rat showed no preferred orientation and are therefore randomly oriented within the tissue. The directions in which the collagen fibrils are oriented determine the directions in which the tissue can best withstand tensile stress.

Type I collagen interacts with phosphatidylcholine vesicles. This conclusion has beenobtained after ultracentrifugation, fluorescence polarization, circular dichroism and differential scanning calorimetry studies. The protein conformation is not modified by the presence of phospholipids. Collagen modifies both the enthalpy change and cooperativity of the phosphatidylcholine phase transition. All these effects exhibit a saturating behavior. The obtained results are interpreted in terms of a peripheral interaction between collagen and the phospholipid vesicles.

The changes in the biochemical composition of basement membrane (BM) inslowtwitch (m. soleus, MS) and fast-twitch (m. rectus femoris, MRF) skeletal muscles of rats were studied during aging and life-time endurance training (treadmill running). The concentrations of the 7S domain of type IV collagen and of the P2 fragment of laminin were determined with radioimmunoassays in the muscles of rats aged 1, 2, 4, 10, and 24 months. The concentration of type IV collagen was higher in MS than in MRF and increased significantly with age. At older ages, the concentration tended to be higher in the MS of trained than untrained rats. The concentration of laminin was significantly higher in MRF than in MS, especially in old age. Consequently, the ratio of type IV collagen to laminin was significantly higher in MS than in MRF, the difference increasing with advancing age. The results show that the Ws in slow muscle are much more collagenous than those in fast muscle which contains, on the contrary, a higher concentration of laminin. This difference seems only partly to be explained by the higher capillarization of slow twitch muscle fibers. Aging and training seem further to distinguish the composition of the BM in slow and fast muscle.

Neutrophils contain a number of proteinases active at neutral pH which are able todegrade extracellular matrices. We have determined the contribution of the major neutral proteinases to human neutrophil-mediated degradation of glomerular basement membrane type IV collagen in an in vitro model of immune complex-induced injury. Studies with proteinase inhibitors showed that with intact neutrophils stimulated by immune complexes trapped within the basement membrane, approximately 70% of the degradation was due to serine proteinases and 30% to metalloproteinases. Identical results were obtained with cell-free medium containing neutrophil granule contents. Elastase accounted for almost all the digestion by serine proteinases with a minimal contribution by cathepsin G. All the metalloproteinase activity was due to gelatinase rather than collagenase, and purified gelatinase was also shown to degrade basement membrane collagen. Hence, gelatinase has activity against type IV collagen and may be able to degrade collagens not cleaved by specific collagenases.

The effect of nerve crush on collagen synthesis in rat sciatic nerve was studied byelectron microscope. The crushed nerves were treated with taxol which is known to increase the amount of cytoplasmic microtubules at the expense of other cell organelles such as rough endoplasmic reticulum and Golgi complexes. The results were compared to those seen in crushed nerves without taxol treatment.

After the injury the amount of collagen fibrils increased at the site of the traumain both groups when compared to intact controls. Thin (30 mn in diameter) collagen firils were often arranged closely to the Schwann cell surface and were connected to deep invaginations in areas where the basal lamina had lost its typical integrity. This was concluded to indicate a probable site of collagen secretion and it provides further evidence that an adult injured nerve Schwann cell is capable of synthesizing fibrous collagen.

In taxol-treated nerves additional, abnormally close connection between thinmicrofibrils of about 10 nm and thin 20-30 nm collagen fibrils appeared in an end-to-end fashion. The microfibrils showed occasional collagenous transverse band like structures. The rough endoplasmic reticulum and Golgi complex play an important role in the posttranslational modifications of the procollagen molecule. Taxol-induced degeneration of cell organelles such as the Golgi complex, which is also essential in the secretion of proteins may thus lead to defective maturation of collagen and may explain partly the altered collagen fibril formation.

Focal adhesions are areas of cell surfaces where specializations of cytoskeletal,membrane and extracellular components combine to produce stable cell-matrix interactions. The morphology of these adhesions and the components identified in them are discussed together with possible mechanisms of their formation.