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This paper compares the organic compositions of the otolith and endolymph of trout and turbot. Irrespective of the method of demineralization (0.5 M EDTA or acetic acid), trout otoliths were found to be largely composed of proteins (48%), collagens (23%), and proteoglycans (29%). Collagen was only detectable in the EDTA-insoluble (0.30 microg/mg) and in the acetic acid-soluble fractions (0.53 microg/mg). The same compounds were found in the endolymph but in different proportions (proteins 85%, collagens 12%, and proteoglycans 3%). It was shown that the distribution of these compounds was not uniform within the endolymph. Proteins, collagens, and amino acids were 4, 10, and 3 times, respectively, more concentrated in the proximal (facing the macula) than the distal side whereas proteoglycans were 10 times more concentrated at the distal side. SDS PAGE analyses of proximal and distal samples of endolymph showed similar patterns suggesting that the spatial gradient of protein is quantitative and not qualitative. SDS PAGE comparison of endolymph and otolith samples showed only two proteins with similar molecular weights. We propose that collagen and protein gradients are involved in the organic matrix formation and otolith calcification process. Endolymphs from both trout and turbot display inhibitions of in vitro calcification although these inhibitions were 50 and 80 times, respectively, less than that of the otoliths. The inhibitory factor probably plays a significant role in the regulation of otolith calcification.
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PMID:Biochemical relationships between endolymph and otolith matrix in the trout (Oncorhynchus mykiss) and turbot (Psetta maxima). 1180 Feb 33

Abnormal gall bladder motor function with delayed emptying and stasis are the contributory factors of gall stone formation. Since collagen is the major contractile protein, this study was designed to find out whether the biochemical and physicochemical changes of collagen contribute to the pathogenesis of gall stone formation. Collagen was isolated from the gall bladder of 25 gall stone patients undergoing cholecystectomy and from that of 20 gall stone free subjects. The levels of total, soluble and insoluble collagen were determined. The activity levels of collagenase (3.4.23.3) and protease (3.4.24.11) were assessed. Levels of susceptibility of collagen to denaturing agents 2 M potassium thiocyanate and 8 M urea were estimated. Aldehyde content, shrinkage temperature and tensile strength were also determined in isolated collagen. SDS-PAGE was carried out and alpha, beta fractions were quantified. The total and insoluble collagen contents were significantly high in gall stone patients. The activity levels of collagenase and protease were significantly low. Elevated levels of lipid peroxides, aldehyde content, shrinkage temperature and tensile strength were observed in gall stone patients. There is a significant elevation in the beta fraction and a decrease in alpha/beta ratio. Ultramicroscopic structure of gall bladder revealed derangement of collagen fibres and altered tissue architecture. The results showed that the qualitative and quantitative alterations in collagen also contribute for the defective contractility and stasis of gall bladder in gall stone patients.
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PMID:Biochemical and physicochemical changes in collagen isolated from the gall bladder of gall stone patients. 1497 98

Collagen VIII is an extracellular matrix macromolecule comprising two polypeptide chains, alpha1(VIII) and alpha2(VIII), that can form homotrimers in vitro and in vivo. Here, recombinant collagen VIII was expressed to study its supramolecular assembly following secretion. Cells transfected with alpha1(VIII) or alpha2(VIII) assembled and secreted homotrimers that were stable in denaturing conditions and had a molecular mass of approximately 180 kDa on SDS-PAGE gels. Co-transfection with prolyl 4-hydroxylase generated homotrimers with stable pepsin-resistant triple-helical domains. Size fractionation of native recombinant collagen VIII molecules expressed with or without prolyl 4-hydroxylase identified urea-sensitive high molecular mass assemblies eluting in the void volume of a Superose 6HR 10/30 column and urea-resistant assemblies of approximately 700 kDa, all of which were composed of homotrimers. Immunofluorescence analysis highlighted the extracellular deposition of recombinant alpha1(VIII)(3), alpha2(VIII)(3), and co-expressed alpha1(VIII)(3)/alpha2(VIII)(3). Microscopy analysis of recombinant collagen VIII identified rod-like molecules of 134 nm in length that assembled into angular arrays with branching angles of approximately 114 degrees and extensive networks. Based on these data, we propose a model of collagen VIII assembly in which four homotrimers form a tetrahedron stabilized by central interacting C-terminal NC1 trimers. Tetrahedrons may then act as building blocks of three-dimensional hexagonal lattices generated by secondary interactions involving terminal and helical sequences.
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PMID:Expression and supramolecular assembly of recombinant alpha1(viii) and alpha2(viii) collagen homotrimers. 1499 May 71

The results of studies carried out over the last few decades indicate a significant involvement of fluoride in connective tissue metabolism. Unfortunately, opinions concerning this issue vary and sometimes are conflicting. Collagen constitutes the main component of the extracellular matrix. Biosynthesis of collagen is a complex, multistage process. Each step in collagen biosynthesis may be affected by exogenous factors. The purpose of the present study was to evaluate the effects of toxic doses of fluoride in drinking water on: 1. The level of COL1A1 gene expression in rat skin; 2. Concentrations of acid-soluble, pepsin-soluble and total collagen isolated from rat skin; 3. Ratio of pepsin-soluble to acid-soluble collagen concentrations; 4. Proportions of alpha2(I)/alpha1(I) and beta/alpha1(I) collagen chains in extracts ofpepsin-soluble collagen. An attempt was made to determine whether fluoride effects are gender-dependent. The experiment was performed in 108 Wistar rats (males and females). Rats were given 60 mg sodium fluoride/dm3 in drinking during 1, 3 or 6 months. Subsequently, animals were sacrificed and blood, femoral bones and fragments of abdominal skin were taken for analysis. Methods used in the study included potentiometry with F- ion-selective electrode, RT-PCR assay, calorimetry, and SDS-PAGE electrophoresis. The results led to the following conclusions: 1. COL1A1 gene expression in the skin of male rats receiving 60 mg NaF/dm3 in drinking water was significantly reduced after 6 months exposure. 2. Fluoride at doses used in the present study basically does not exert an effect on the concentration of each collagen form in rat skin, ratio of pepsin-soluble to acid-soluble collagen concentrations, and relative proportions of some collagen chains in the pepsin-soluble collagen extract. 3. Male rats were more sensitive to fluoride action in the present study as compared with females. 4. Further research on fluoride penetration to the skin in experimental animals is needed in order to elucidate the relatively low toxicity of fluoride in this tissue.
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PMID:[Evaluation of toxic doses of fluorine on expression of collagen genes and synthesis of some collagen proteins in rat skin]. 1555 39

Collagen X is a short chain collagen expressed specifically by the hypertrophic chondrocytes of the cartilage growth plate during endochondral bone formation. Accordingly, COL10A1 mutations disrupt growth plate function and cause Schmid metaphyseal chondrodysplasia (SMCD). SMCD mutations are almost exclusively located in the NC1 domain, which is crucial for both trimer formation and extracellular assembly. Several mutations are expected to reduce the level of functional collagen X due to NC1 domain misfolding or exclusion from stable trimer formation. However, other mutations may be tolerated within the structure of the assembled NC1 trimer, allowing mutant chains to exert a dominant-negative impact within the extracellular matrix. To address this, we engineered SMCD mutations that are predicted either to prohibit subunit folding and assembly (NC1del10 and Y598D, respectively) or to allow trimerization (N617K and G618V) and transfected these constructs into 293-EBNA and SaOS-2 cells. Although expected to form stable trimers, G618V and N617K chains (like Y598D and NC1del10 chains) were secreted very poorly compared with wild-type collagen X. Interestingly, all mutations resulted in formation of an unusual SDS-stable dimer, which dissociated upon reduction. As the NC1 domain sulfhydryl group is not solvent-exposed in the correctly folded NC1 monomer, disulfide bond formation would result only from a dramatic conformational change. In cells expressing mutant collagen X, we detected significantly increased amounts of the spliced form of X-box DNA-binding protein mRNA and up-regulation of BiP, two key markers for the unfolded protein response. Our data provide the first clear evidence for misfolding of SMCD collagen X mutants, and we propose that solvent exposure of the NC1 thiol may trigger the recognition and degradation of mutant collagen X chains.
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PMID:Misfolding of collagen X chains harboring Schmid metaphyseal chondrodysplasia mutations results in aberrant disulfide bond formation, intracellular retention, and activation of the unfolded protein response. 1569 17

Native and chemically stabilized porcine pericardium tissue was imaged by the contact mode atomic force microscopy (AFM), in air. Chemically stabilized pericardium is used as a tissue-derived biomaterial in various fields of the reconstructive and replacement surgery. Collagen type I is the main component of the fibrous layer of the pericardium tissue. In this study, the surface topography of collagen fibrils in their native state in tissue and after chemical stabilization with different cross-linking reagents: glutaraldehyde (GA), dimethyl suberimidate (DMS) and tannic acid (TA) was investigated. It has been found that chemical stabilization causes considerable changes in the surface topography of collagen fibrils as well as in the spatial organization of the fibrils within the tissue. The observed changes in the D-spacing pattern of the collagen fibril correspond to the formation of intrafibrilar cross-links, whereas formation of interfibrilar cross-links is mainly responsible for the observed tangled spatial arrangement of fibrils and crimp structure of the tissue surface. The crimp structure was distinctly seen for the GA cross-linked tissue. Surface heterogeneity of the cross-linking process was observed for the DMS-stabilized tissue. SDS-PAGE electrophoresis was performed in order to evaluate the stabilization effect of the tissues treated with the cross-linking reagents. It has been found that stabilization with DMS, GA or TA enhances significantly the tissue resistance to SDS/NaCl extraction. The relation between the tissue stability and changes in the topography of the tissue surface was interpreted in terms of different nature of cross-links formed by DMS, GA and TA with collagen.
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PMID:Atomic force microscopy investigation of chemically stabilized pericardium tissue. 1575 Jun 84

Nonenzymatic glycation of proteins, leading to chemical modification and cross-linking are of importance in the pathology of diabetic complications. We studied the effect alpha-lipoic acid (LA) on the content and characteristics of the protein collagen from skin of high-fructose fed rats. The rats were divided into 4 groups of 6 each. Two groups of rats were fed with a high fructose diet (60 g/100 g diet) and administered either LA (35 mg/kg b.w., i.p) (FRU+LA) or 0.2 ml vehicle (saline) (FRU) for 45 days. The other 2 groups were fed with control diet containing starch (60 g/100 g diet) and administered either saline (CON) or lipoic acid (CON+LA). The rats were maintained for 45 days and then sacrificed. Plasma glucose, insulin, fructosamine, protein glycation, and blood glycated hemoglobin (HbA1C) were measured. Collagen was isolated from skin and the physicochemical properties of collagen were studied. Fructose administration caused accumulation of collagen in skin. Extensive cross-linking was evidenced by enhanced glycation and AGE-linked fluorescence. Increased peroxidation and changes in physicochemical properties such as shrinkage temperature, aldehyde content, solubililty pattern, susceptibility to denaturing agents were observed in fructose-fed rats. SDS gel pattern of collagen from these rats showed elevated beta component of type I collagen. These changes were alleviated by the simultaneous administration of LA. Administration of LA to fructose-fed rats had a positive influence on both quantitative and qualitative properties of collagen. The results suggest a mechanism for the ability of LA to delay diabetic complications.
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PMID:Fructose diet-induced skin collagen abnormalities are prevented by lipoic acid. 1576 37

Porcine small intestinal submucosa (SIS) was shown to be an effective bioscaffold in enhancing the mechanical properties of healing medial collateral ligaments (MCL). The purpose of this study was to investigate whether there are corresponding improvements in morphology and tissue compositions. Fourteen rabbits were equally divided into two groups. In the SIS-treated group, a 6 mm gap was surgically created in the right MCL and a layer of SIS was sutured covering the gap. For the nontreated group, the gap-injured MCLs remained untreated. All the left MCLs were sham operated and used as controls. At 12 weeks, the status of collagen types I and V was evaluated with immunofluorescent staining. The collagen type V/I ratios were obtained using SDS-PAGE. Collagen fibril diameters were calculated from the transmission electron micrographs. The results revealed that in the SIS-treated group, the collagen fibers were more regularly aligned as were the cell nuclei. The collagen fibril diameters were 22.2% larger and the ratio of collagen type V/I was 28.4% lower than those for the nontreated group (p < 0.05). These improvements in the morphological characteristics and biochemical constituents of healing MCLs following SIS treatment are the likely reasons for improved mechanical properties.
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PMID:Treatment with bioscaffold enhances the the fibril morphology and the collagen composition of healing medial collateral ligament in rabbits. 1649 52

A chronic administration of isoproterenol hydrochloride (60 mg/kg body weight; 30 days) alters the collagen metabolism in denervated gastrocnemius muscle of mice. Hydroxyproline assay for collagen showed an increase in collagen content by 47%, 44%, and 61% in innervated gastrocnemius + drug, denervated control, and denervated + drug, respectively, in gastrocnemius muscles after 30 days of drug administration. Collagen proliferation is beta-agonist (isoproterenol) specific confirmed with the simultaneous administration of beta-antagonist propranolol (100 mg/kg body weight; 30 days). Van Gieson staining showed heavy collagen proliferation in the epimysium region of the muscle section and adventitia of blood vessels and some specialized regions. However, denervated gastrocnemius muscle represented a heavy collagen proliferation in the endomysium region, which also is probably responsible for extensive collagen proliferation in denervated muscle after drug administration. The SDS-PAGE of pepsin-soluble collagen revealed five bands from origin to the point of migration, gamma, beta1, beta2, alpha1, and alpha2. The SDS-PAGE of CNBr-treated pepsin-insoluble collagen pointed toward the more prominent remodeling of collagen metabolism in the beta-agonist-induced denervated gastrocnemius muscle after drug administration. From the present study, we can conclude that beta-agonist, isoproterenol hydrochloride, augments collagen proliferation in innervated as well as in denervated gastrocnemius muscle.
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PMID:Remodeling of extracellular matrix protein, collagen by beta-adrenoceptor stimulation and denervation in mouse gastrocnemius muscle. 1677 16

Collagen, fibrin and albumin are popular proteins for making biological scaffolds for tissue engineering because of their biocompatibility, biodegradability, and availability. A major drawback of biological protein-based biomaterials is the limited control over their physical and biodegradation properties. Our laboratory has been developing new protein-based biomaterials with tunable properties without the use of cytotoxic protein cross-linking techniques. We describe the formation and assembly of photopolymerizable biomimetic hydrogel scaffolds made from protein-polymer conjugates of poly(ethylene glycol) (PEG) and collagen, fibrin or albumin. The conjugation of PEG to these proteins (PEGylation) was verified by SDS-PAGE and the polymerization reaction into a hydrogel network was confirmed by shear rheometry. The differences in rheology and swelling characteristics of the three hydrogel materials underscore the importance of the molecular relationship between the PEG and the protein constituent in this protein-polymer arrangement. The biofunctionality of the PEGylated collagen and fibrinogen hydrogels sustained both cell adhesion and proteolytic degradation that enabled 3-D cell spreading and migration within the hydrogel network. PEG-albumin hydrogels exhibited poor cell spreading and migration by virtue of the fact that the albumin backbone lacks any known cell adhesion sites. Despite differences in the biological and structural composition of the PEGylated fibrinogen and collagen hydrogels, the rate of cellular migration within each material was not significantly different.
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PMID:Protein-polymer conjugates for forming photopolymerizable biomimetic hydrogels for tissue engineering. 1757 8


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