Conformation Of Collagen Research Articles

Production of EGF–collagen chimeric protein which shows the mitogenic activity

Collagen has been utilized as a natural biomaterial because of its high biocompatibility, adhesiveness to cells and tissues, and biodegradability. The present study developed a recombinant technology to confer a mitogenic activity on type III collagen by fusing it to epidermal growth factor (EGF) at the collagen’s N-terminus. The chimeric protein of EGF–collagen was synthesized in insect cells by the baculovirus-insect cell expression system. The fusion protein was shown to hold the triple helical conformation of collagen and the mitogenic activity of EGF. It was also demonstrated that the chimeric protein can be immobilized on tissue culture dishes as a fibrous form and in collagen fibrils without abolishing the original mitogenic activity of EGF. This fusion protein can be utilized as a biocompatible, biodegradable, and adhesive fibrous mitogen for a variety of purposes in the area of tissue engineering.

Effect of dentin primers on the morphology, molecular composition and collagen conformation of acid-demineralized dentin in situ

Objectives: The purpose of this study was to assess the effect of two commercial primers and distilled water on the morphology, molecular composition and collagen conformation of acid-demineralized dentin in situ. Methods: Dentin specimens etched with Scotchbond Etchant were imaged by tapping mode AFM and analyzed by MIR-FTIR spectroscopy. They were then primed with Scotchbond Multi-Purpose Plus Primer, Scotchbond 1 Adhesive or distilled water and imaged and analyzed again. The chemical modifications induced on the uppermost 2 μm of primed dentin were studied after water and original primer subtraction. The conformational changes of type I collagen at this region were evaluated by deconvoluting the amide I band components. The absorbance ratio A n(1655/1627) was used to semiquantitatively assess, on a relative basis, the extent of collagen denaturation. Results: All the priming treatments swelled the collapsed dentin collagen left after etching. No evidence of primary bonding was found after priming treatments, while approximately 50% of the conditioned dentin collagen appeared denatured. Treatment with distilled water did not change the status of denatured collagen, however, application of the commercial primers refolded the α-helix to ≈95% of the extent found on the native reference dentin. Significance: The dynamic response of dentin collagen to demineralization and priming treatments reveals the critical role of some primers in rapidly restoring the conformational status of acid-denatured collagen. Implementation of reactive adhesive groups in α-helix recovery may provide an associative means of modifying the mechanical properties of the demineralized collagen based on the extent of their intermolecular bonding.

Interaction of collagen molecules from the aspect of fibril formation: acid-soluble, alkali-treated, and MMP1-digested fragments of type I collagen.

Collagen type I extracted with acid or digested with pepsin forms fibrils under physiological conditions, but this ability is lost when the collagen is treated with alkaline solution or digested with matrix metalloproteinase 1 (MMP1). When acid-soluble collagen was incubated with alkali-treated collagen, the fibril formation of acid-soluble collagen was inhibited. At 37 degrees C, at which alkali-treated collagen is denatured, the lag time was prolonged but the growth rate of fibrils was not affected. At 30 degrees C, at which the triple helical conformation of alkali-treated collagen is retained, the lag time was prolonged and the growth rate reduced. Heat-denatured alkali-treated collagen and MMP1-digested fragments have no inhibitory effect on the fibril formation of acid-soluble collagen. This means that the triple helical conformation and the molecular length are important factors in the interaction of collagen molecules and that alkali-treated collagen acts as a competitive inhibitor for fibril formation of collagen. We found that alkali-treated collagen and MMP1-digested fragments form fibrils that lack the D periodic banding pattern and twisted morphology under acidic conditions at the appropriate ionic strength. We also calculated the relative strengths of hydrophobic and electrostatic interactions between collagen molecules. When the hydrophobic interaction between linear collagen molecules was considered, we found a pattern of periodic maximization of the interactive force including the D period. On the other hand, the electrostatic interaction did not show the periodic pattern, but the overall interaction score affected fibril formation.

Binding of the periodontal pathogen Actinobacillus actinomycetemcomitans to extracellular matrix proteins.

The interaction of Actinobacillus actinomycetemcomitans, an important pathogen implicated in juvenile and adult periodontitis, with collagenous and noncollagenous proteins of the extracellular matrix was investigated. A. actinomycetemcomitans SUNY 465 bound to immobilized type I, II, III and V but not type IV collagen. Binding to immobilized collagen was saturable and concentration dependent. This interaction could not be inhibited by soluble collagen, suggesting that binding was dependent on a specific collagen conformation. Bacteria grown anaerobically exhibited decreased collagen-binding activity as compared with organisms grown acrobically. Bacterial outer membrane proteins were essential for binding to collagen. A actinomycetemcomitans SUNY 465 also bound to immobilized fibronectin. In contrast, bacteria did not bind to fibrinogen, bone sialoprotein, alpha 2-HS glycoprotein or albumin. The mechanism of the interaction with fibronectin was more complex, possibly involving both protein and nonproteinaceous components. The majority of other A. actinomycetemcomitans strains tested bound to extracellular matrix proteins in a manner similar to SUNY 465 but with minor variation. These results demonstrate that A. actinomycetemcomitans binds to proteins found in connective tissue. The interaction with extracellular matrix proteins may contribute to the virulence of this pathogen at oral and extraoral sites of infection.

Simple Collagen-Like Peptides Support Platelet Adhesion Under Static But Not Under Flow Conditions: Interaction Via α2β1 and von Willebrand Factor With Specific Sequences in Native Collagen Is a Requirement to Resist Shear Forces

The aim of this study was to define the need for specific collagen sequences and the role of their conformation in platelet adhesion to collagen under both static and flow conditions. We recently reported that simple triple-helical collagen-related peptides (CRPs), GCP*(GPP*)10GCP*G and GKP*(GPP*)10GKP*G (single-letter amino acid code, P* = hydroxyproline; Morton et al,Biochem J 306:337, 1995) were potent stimulators of platelet activation and were able to support the adhesion of gel-filtered platelets examined under static conditions. The present study investigated whether these same peptides were able to support platelet adhesion under more physiologic conditions by examining static adhesion with platelet-rich plasma (PRP) and adhesion under flow conditions. In the static adhesion assay, we observed 20% surface coverage with platelet aggregates. In marked contrast, there was a total lack of adhesion under flow conditions examined at shear rates of 50 and 300 s−1. Thus, the interaction of platelets with the CRPs is a low-affinity interaction unable on its own to withstand shear forces. However, the addition of CRPs to whole blood, in the presence of 200 μmol/L D-arginyl-glycyl-L-aspartyl-L-tryptophan (dRGDW) to prevent platelet aggregation, caused an inhibition of about 50% of platelet adhesion to collagens I and III under flow. These results suggest that the collagen triple helix per se, as defined by these simple collagen sequences, plays an important contributory role in the overall process of adhesion to collagen under flow. The monoclonal antibody (MoAb) 176D7, directed against the α2 subunit of the integrin α2β1, was found to inhibit static platelet adhesion to monomeric but not fibrillar collagens I and III. However, under flow conditions, anti-α2 MoAbs (176D7 anf 6F1) inhibited adhesion to both monomeric and fibrillar collagens, indicating that α2β1 is essential for adhesion to collagen under flow, independent of collagen conformation, whether monomeric or polymeric. To obtain further insight into the nature of the different adhesive properties of CRPs and native collagen, we investigated the relative importance of von Willebrand factor (vWF) and the integrin α2β1 in platelet adhesion to collagen types I and III, using the same shear rate (300 s−1) as used when testing CRPs under flow conditions. Our results, together with recent data of others, support a two-step mechanism of platelet interaction with collagen under flow conditions. The first step involves adhesion via both the indirect interaction of platelet glycoprotein (GP) Ib with collagen mediated by vWF binding to specific vWF-recognition sites in collagen and the direct interaction between platelet α2β1 and specific α2β1-recognition sites in collagen. This suffices to hold platelets at the collagen surface. The second step occurs via another collagen receptor (thought to be GPVI) that binds to simple collagen sequences, required essentially to delineate the collagen triple helix. Recognition of the triple helix leads to strengthening of attachment and platelet activation.

Simple Collagen-Like Peptides Support Platelet Adhesion Under Static But Not Under Flow Conditions: Interaction Via α2β1 and von Willebrand Factor With Specific Sequences in Native Collagen Is a Requirement to Resist Shear Forces

AbstractThe aim of this study was to define the need for specific collagen sequences and the role of their conformation in platelet adhesion to collagen under both static and flow conditions. We recently reported that simple triple-helical collagen-related peptides (CRPs), GCP*(GPP*)10GCP*G and GKP*(GPP*)10GKP*G (single-letter amino acid code, P* = hydroxyproline; Morton et al,Biochem J 306:337, 1995) were potent stimulators of platelet activation and were able to support the adhesion of gel-filtered platelets examined under static conditions. The present study investigated whether these same peptides were able to support platelet adhesion under more physiologic conditions by examining static adhesion with platelet-rich plasma (PRP) and adhesion under flow conditions. In the static adhesion assay, we observed 20% surface coverage with platelet aggregates. In marked contrast, there was a total lack of adhesion under flow conditions examined at shear rates of 50 and 300 s−1. Thus, the interaction of platelets with the CRPs is a low-affinity interaction unable on its own to withstand shear forces. However, the addition of CRPs to whole blood, in the presence of 200 μmol/L D-arginyl-glycyl-L-aspartyl-L-tryptophan (dRGDW) to prevent platelet aggregation, caused an inhibition of about 50% of platelet adhesion to collagens I and III under flow. These results suggest that the collagen triple helix per se, as defined by these simple collagen sequences, plays an important contributory role in the overall process of adhesion to collagen under flow. The monoclonal antibody (MoAb) 176D7, directed against the α2 subunit of the integrin α2β1, was found to inhibit static platelet adhesion to monomeric but not fibrillar collagens I and III. However, under flow conditions, anti-α2 MoAbs (176D7 anf 6F1) inhibited adhesion to both monomeric and fibrillar collagens, indicating that α2β1 is essential for adhesion to collagen under flow, independent of collagen conformation, whether monomeric or polymeric. To obtain further insight into the nature of the different adhesive properties of CRPs and native collagen, we investigated the relative importance of von Willebrand factor (vWF) and the integrin α2β1 in platelet adhesion to collagen types I and III, using the same shear rate (300 s−1) as used when testing CRPs under flow conditions. Our results, together with recent data of others, support a two-step mechanism of platelet interaction with collagen under flow conditions. The first step involves adhesion via both the indirect interaction of platelet glycoprotein (GP) Ib with collagen mediated by vWF binding to specific vWF-recognition sites in collagen and the direct interaction between platelet α2β1 and specific α2β1-recognition sites in collagen. This suffices to hold platelets at the collagen surface. The second step occurs via another collagen receptor (thought to be GPVI) that binds to simple collagen sequences, required essentially to delineate the collagen triple helix. Recognition of the triple helix leads to strengthening of attachment and platelet activation.

Effect of acidic conditioners on dentin morphology, molecular composition and collagen conformation in situ

Objective: The aim of the study was to evaluate the effect of some acidic conditioners on dentin morphology, molecular composition and collagen conformation in situ. Methods: Smear layer-covered dentin specimens prepared from third molars immediately after extraction were imaged by tapping mode AFM and analyzed by MIR-FTIR spectroscopy. The same specimens were subjected to conditioning treatments with CA Agent (Kuraray), Scotchbond Etchant (3M Dental Products) and Scotchbond MP Etchant (3M Dental Products) gels and then imaged and analyzed again. The extent of dentin decalcification at the uppermost 2 μm region was calculated from the percentage reduction in the -PO 4/amide I peak area ratio of conditioned specimens relative to their individual smear layer-covered references. These results were compared by ANOVA and Scheffe´statistical analyses. The conformational changes of dentin type I collagen at the region were studied qualitatively by deconvoluting the amide I bands of MIR-FTIR spectra and assigning the band components to carbonyl hydrogen bonding states related to the α-helix structure. Results: All the conditioners removed the smear layer, funneled the tubules, increased the intertubular roughness and contaminated the dentin surfaces with residues from irreversibly adsorbed thickening agents. Conditioned dentin surfaces showed a reduction in orthophosphates and carbonates and an increase in amide I, II and III groups. CA Agent manifested a significantly lower extent of dentin decalcification than Scotchbond etchants (p < 0.05). Collagen conformational changes involved a decrease in intermolecular hydrogen bonded amide I carbonyls associated with the α-helix structure and enhancement of imide carbonyls hydrogen bonded to water, which suggest collagen denaturation. Significance: Apart from dentin decalcification, the acidic conditioners induced considerable changes on dentin collagen conformation mostly associated with denaturation processes. In addition, irreversibly adsorbed residual thickeners substantially modified the morphology and composition of dentin surfaces. These findings show the complex interaction pathways between conditioners and dentin surfaces and the great potential of modern in situ imaging and analysis techniques in probing these interactions.

Biochemical alterations in collagen IV induced by in vitro glycation.

Non-enzymic interactions of carbohydrates and proteins are a major feature of cumulative modification in basement membranes in the course of diabetic microvascular complications. To evaluate the significance of both glycation and glycoxidation reactions for subsequent alterations of biochemical properties, we examined the effects of in vitro glycation on distinct collagen IV domains under different experimental conditions. The 7 S domain and the major triple-helical domain from human placental collagen IV were incubated for various time intervals up to 14 days at 37 degrees C in the presence of different concentrations of either glucose or ribose under oxidative and antioxidative conditions. Carbohydrate-induced non-enzymic modification in two collagen IV domains was revealed by increased cross-linking and fluorescence. In addition, these non-enzymic modifications apparently have a major impact on molecular conformation and thermal stability of collagen IV, which in turn might influence both cell-matrix interactions and matrix assembly.

Solid-phase synthesis of triple-helical collagen-model peptides

The triple-helical conformation of collagen has been proposed to be important for mediation of cellular activities, such as adhesion and activation, extracellular matrix assembly, and enzyme function. We have developed synthetic protocols that allow for the study of biological activities of specific collagen sequences in triple-helical conformation. These methods primarily involve solid-phase assembly and covalent linkage of three peptide chains. The resultant triple-helical peptides have sufficient thermal stabilities to permit structural and biological characterization under physiological conditions. The present article critically reviews the various approaches for constructing synthetic triple-helices.

Alpha-methyl-proline restores normal levels of bone collagen type i synthesis in ovariectomized rats

Collagen type I is the major protein of bone matrix and significantly reduced in osteoporosis. We tested the effect of alpha — methyl — proline on collagen synthesis in the model of the ovariectomized rat. Collagen synthesis was studied at the transcriptional level using Northern and dot blotting and at the protein level using hydroxyproline determination and a specific dye binding collagen assay. Alpha — methyl — proline treatment significantly increased collagen synthesis as compared to untreated ovariectomized and estradiol treated ovariectomized rats and restored collagen synthesis to levels of sham operated rats. Proline analogues were described to stimulate procollagen synthesis at the transcriptional level, however, if incorporated, lead to negative collagen production due to rapid intracellular degradation of the deficient collagen. Our synthesized analogue is not being incorporated, thus not interfering with collagen conformation and can therefore induce collagen production.

Extracellular Matrix Binding Properties of Recombinant Fibronectin Type II-like Modules of Human 72-kDa Gelatinase/Type IV Collagenase: HIGH AFFINITY BINDING TO NATIVE TYPE I COLLAGEN BUT NOT NATIVE TYPE IV COLLAGEN

72-kDa gelatinase/type IV collagenase is an important matrix metalloproteinase in the degradation of basement membranes and denatured collagens (gelatin). These proteolytic processes are required for pathologic tissue destruction and physiologic tissue remodeling. To investigate the molecular determinants of substrate specificity of this enzyme, a 21-kDa domain of 72-kDa gelatinase, consisting of three tandem fibronectin type II-like modules, was expressed in Escherichia coli. Similar to full-length 72-kDa gelatinase and the type II modules in fibronectin, the recombinant (r) fibronectin-like domain of this proteinase bound denatured type I collagen with an apparent Kd in the micromolar range. This domain, designated the collagen-binding domain (rCBD123), possesses at least two collagen-binding sites that can each be simultaneously occupied. rCBD123 also avidly bound elastin and denatured types IV and V collagens, but neither native types IV and V collagens nor fibronectin, all of which are substrates of the enzyme. Although 72-kDa gelatinase is involved in basement membrane degradation, rCBD123 also did not bind reconstituted basement membrane, laminin, or SPARC. Native type I collagen, which is not degraded by 72-kDa gelatinase, competed with gelatin for a shared binding site on rCBD123. rCBD123 also displaced full-length 72-kDa gelatinase bound to native type I collagen, further demonstrating that the collagen binding properties of the recombinant domain closely mimicked those of the full-length enzyme. Since rCBD123 showed reduced binding to pepsin-cleaved type I collagen, either or both of the collagen telopeptide ends contain recognition sites for the 72-kDa gelatinase fibronectin-like domain. This was confirmed by the avid binding of rCBD123 to the alpha 1(I) collagen cyanogen bromide fragment CB2 from the NH2-terminal telopeptide. rCBD123 also bound alpha 1(I)-CB7, which encompasses the fibronectin-binding site, and to alpha 1(I)-CB8, a fragment not bound by fibronectin. Thus, type I collagen contains multiple binding sites for rCBD123 which are partially masked by the triple helical conformation of native collagen and fully exposed upon unfolding of the triple helix. The potential of the fibronectin-like collagen binding domain of 72-kDa gelatinase to bind extracellular matrix proteins may facilitate enzyme localization in connective tissue matrices.

Ventricular remodeling in heart failure: the role of myocardial collagen.

Collagen which is present in the myocardium in relatively small amounts is the most abundant structural protein of the connective tissue network. Its structural organization consists of a complex weave of collagen fibers that surrounds and interconnects myocytes, groups of myocytes, muscle fibers and muscle bundles. The conformation of interstitial fibrillar collagen makes it highly resistant to degradation by all proteinases other than specific collagenases. In hearts with myocardial damage secondary to myocardial infarction, chronic ischemia, inflammation, or cardiomyopathy, a complex sequence of compensatory events occur that eventually result in an adverse left ventricular remodeling. This continual state of remodeling is characterized by persistent collagenase activity, fibrillar collagen degradation, and progressive myocyte loss. The net effect is a shift in the balance between collagen synthesis and degradation which leads to an inadequate fibrillar collagen matrix, progressive ventricular dilatation and sphericalization with wall thinning and eventual congestive heart failure.

Cellular recognition processes and type IV collagen conformation

Cellular recognition processes and type IV collagen conformation

Conformation dependence of integrin-type II collagen binding. Inability of collagen peptides to support alpha 2 beta 1 binding, and mediation of adhesion to denatured collagen by a novel alpha 5 beta 1-fibronectin bridge.

The mechanism of interaction of chondrocytic cells with cartilage-specific type II collagen has been examined using HCS-2/8 human chondrosarcoma cells as a model system. By the criteria of specific collagen secretion and integrin expression profile, HCS-2/8 have a similar differentiated phenotype to normal chondrocytes and are therefore a good model system. HCS-2/8 cells were able to attach and spread on both native and heat-denatured pepsinised type II collagen, and assays using denatured cyanogen bromide fragments apparently localised the major cell binding site to the CB10 fragment. However, when they were used as soluble inhibitors, cyanogen bromide fragments were found to block adhesion to denatured collagen, but had no effect on either attachment or spreading on the native molecule. The inability of cyanogen bromide fragments to reproduce the cell binding site of native collagen demonstrated a strict dependence on collagen conformation. This was also reflected in the receptors that were employed by HCS-2/8 cells for binding to type II collagen: binding to native collagen was mediated by the integrin alpha 2 beta 1 while binding to denatured collagen was mediated by a novel alpha 5 beta 1-fibronectin bridge. The identification of this bridge adds to the mechanisms by which cells can bind to denatured collagens. The previously characterised KDGEA active site peptide from type I collagen was found to be inactive as an inhibitor of type II collagen-mediated adhesion. The implications of these findings for the strategies used to identify adhesive active sites within collagens are discussed. In particular, these data suggest that, unlike other integrin ligands, a synthetic peptide-based approach is not suitable for the identification of collagen active sites.

Characterization of Thrombospondin Binding to Collagen (Type I) Fibres: Role of Collagen Telopeptides

We have shown that thrombospondin (tsp), like fibronectin (fn) and von Willebrand factor (vWf), exhibits a rapid, specific and saturable binding to collagen type I fibres (from bovine tendon). The level of binding at saturation is very similar to that of vWf. As with fn and vWf, the interaction is ionic in character and appears to occur by a polyvalent mechanism since there is little inhibition of interaction by monomeric collagen. The conformation of tsp, like that of fn and vWf, is important since denaturation causes reduced complexing. Furthermore, conformational changes in tsp due to the presence of Ca++ can modulate the amount of complex formed under physiological conditions. Tsp, like vWf but in contrast to fn, shows little affinity for denatured fibres emphasizing the importance of collagen conformation. Pepsin digestion suggests an important role for collagen telopeptides; vWf- and fn-binding sites are located more within the collagen triple helix. Comparison of the effect on binding after leucine aminopeptidase or carboxypeptidase digestion suggests involvement of the N- rather than C-terminal telopeptides. No evidence was found for a role for fn, the proteoglycan PG2 or collagen type V, which could be present in type I fibres, in mediating the interaction between tsp and the fibres. VWf did not inhibit the interaction of tsp, but fn did slightly when tested in large excess. This suggests separate binding sites in collagen for all three ligands since fn and vWf are also known to bind independently of each other.

Platelet-reactive sites in collagens type I and type III. Evidence for separate adhesion and aggregatory sites

The adhesion of human and rabbit platelets to collagens and collagen-derived fragments immobilized on plastic was investigated. Adhesion appeared to be independent of collagen conformation, since similar attachment occurred to collagen (type I) in monomeric form, as fibres or in denatured state. The adhesion of human platelets was stimulated to a variable degree by Mg2+, but rabbit platelet adhesion showed little if any dependence on this cation. Collagens type I, III, V and VI were all able to support adhesion, although that to collagen type V (native) was lower than that to the other collagens. Adhesion to a series of peptides derived from collagens I and III was measured. Attachment did not require the presence of peptides in triple-helical configuration. The extent of adhesion ranged from relatively high, as good as to the intact parent collagen molecule, to little if any adhesive activity beyond the non-specific (background) level. The existence of very different degrees of activity suggests that platelet adhesion is associated with specific structural sites in the collagen molecule. Adhesion in many instances was essentially in accord with the known platelet-aggregatory activity of individual peptides. However, two peptides, alpha 1(I)CB3 and alpha 1(III)CB1,8,10,2, exhibited good adhesive activity although possessing little if any aggregatory activity. Of particular interest, despite its near-total lack of aggregatory activity, adhesion to peptide alpha 1(I)CB3 was as good as that to the structurally homologous peptide alpha 1(III)CB4, in which is located a highly reactive aggregatory site. This implies that platelet adhesion to collagen may involve sites in the collagen molecule distinct from those more directly associated with aggregation.

Different behavior of type I and type I-trimer collagen in neutral sodium chloride solutions

Type I and type I-trimer collagen, isolated from ductal infiltrating carcinoma of the human breast, have been tested for their behavior in neutral NaCl solutions. Evident diversities in their rate of precipitation at different saline concentrations have been found, since type I-trimer collagen precipitates at low NaCl molarity while type I collagen is mostly recovered in 2.6–3.6 m NaCl solutions. The native conformation of homotrimer collagen is proved by its ability to produce segment long-spacing crystallites and native-type fibrils.

Conformation of interstitial collagen of bovine rumen and skin.

SummarySamples of ruminal and skin mucosa of 2.5 to 3.0 years old bovines were examined for protein extractability, aldehyde content, ultraviolet absorption spectra, optical rotation and electrophoretic behaviour using consecutive extractions with water, saline and acid solutions. The proteins of ruminal mucosa were more easily extracted by solvents of less ionic strength and have the highest proportion of aldehydes. The less negative rotatory dispersion, like the results of extractability of the ruminal samples, indicates a less helical content in rumen collagen than in that of the skin. By comparison of results obtained with foetal ruminal samples using a similar approach, it was established that the helical content of adult rumen collagen is fully attained in the full‐term foetus.ZusammenfassungKonformation des interstitiellen Kollagens im Pansen und in der Haut des RindesProben von Pansenmucosa und Haut wurden zur Bestimmung der Proteinextrahierbarkeit, des Aldehydgehalts, der Ultraviolettabsorptionsspektren, der Lichtdrehung sowie des elektrophoretischen Verhaltens zunächst mit Wasser, dann mit NaCl‐Lösung und sauren Lösungen extrahiert. Die Proteine der Pansenmucosa ließen sich am leichtesten mit Lösungen geringer Ionenstärke extrahieren. Sie wiesen einen sehr hohen Aldehydgehalt auf. Die geringere negative Lichtdrehung sowie das Extraktionsverhalten der Pansenmucosaproben weisen im Vergleich zu den Hautproben auf eine weniger ausgeprägte helikale Struktur des Pansen‐Kollagens hin. Vergleichsuntersuchungen ergaben, daß die helikale Struktur des Pansen‐Kollagens des reifen Foetus bereits derjenigen des Pansen‐Kollagens adulter Rinder entspricht.ResumenConformación del colágeno intersticial de rumen y piel bovinasSe obtuvieron muestras de mucosa ruminal y de piel de bovinos entre 2,5 a 3,0 años de edad. En consecutivos extractos acuosos, salinos y ácidos de estas muestras se determinó: extractabilidad de proteínas, contenido de aldehídos, espectros de absorción ultravioleta, dispersión rotatoria óptica y comportamiento electroforético. Se observó que las proteínas de la mucosa ruminal fueron más fácilmente extraídas por solventes de menor fuerza iónica, y tenían una mayor proporción de aldehídos. La dispersión rotatoria óptica menos negativa junto a los resultados de extractabilidad de las muestras de rumen indican un menor contenido helicoidal en el colágeno ruminal comparado con el de piel. Por comparación con los resultados obtenidos de muestras de mucosa ruminal fetal bajo similares condiciones se pudo determinar que el contenido helicoidal del colágeno ruminal adulto se establece ya en los fetos a término.

Effects of water-extractable components from bis-GMA-based methacrylate resin on collagen from bovine tendon

This collagen was partially dissolved when suspended in solutions containing water-extractable components from bis-GMA-based resins (WECR) for 120 h at 37 °C. The remaining insoluble collagen was more susceptible to trypsin than the untreated one. Thus WECR may cause changes in collagen conformation similar effects may occur in dentine collagen exposed to the resins during restoration.

Collagen-dependent growth suppression and changes in the shape of human dermal fibroblasts.

This study was designed to investigate the effects of collagen on the growth and cellular shape of cultured human fibroblasts. The fibroblasts grown in the presence of collagen assumed a slim, rod-like form with abundant cytoplasmic protrusions, while the cells on a plain dish showed flat forms with fewer cytoplasmic protrusions. Incorporation of [3H]thymidine was remarkably suppressed in the cells grown on collagen when compared with the fibroblasts on the plain dish. Specific cellular shape and suppressed DNA synthesis showed dependence on the steric conformation of native collagen, because collagen-specific effects on fibroblasts were completely abolished when 60% of the helix content was lost by heat denaturation. These collagen-dependent features of the cells disappeared when the collagen-containing medium was treated with bacterial collagenase. Growth of fibroblasts in contact with collagen was suppressed as compared to that on the plastic dish. These results indicate the importance of the native conformation of collagen in the interaction of collagen and fibroblasts.