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PubMed1977

Transitions in collagen types during matrix-induced cartilage, bone, and bone marrow formation.

The localization of types I, II, and III collagens during bone matrix-induced sequential differentiation of cartilage, bone, and bone marrow was studied by specific immunofluorescence. Subcutaneous transplantation of coarse powders of demineralized rat bone matrix into allogeneic recipients resulted in new bone formation. After a transient appearance of polymorphonuclear leukocytes in the implant, fibroblasts appeared in close continguity to the matrix on day 3. Type III collagen was then localized as a fine network around the invading fibroblasts. On days 4--6 smaller amounts of type I were also detected around these proliferating cells. With the onset of chondrogenesis, type II collagen was detected in the cartilage matrix on day 6 and persisted until the early stages of bone formation. Vascular invasion of the implant was accompanied by osteogenesis on day 10. Type I collagen was demonstrated in the newly deposited bone matrix coating the surfaces of cartilage spicules and particles of implanted bone powder. On day 17 and thereafter, type III collagen was localized as a fibrous array around nests of hematopoietic cells.

Animals↗
PubMed1978

Calcification of isolated matrix vesicles and reconstituted vesicles from fetal bovine cartilage.

Ca deposition by isolated matrix vesicles from fetal calf growth plate cartilage and by a deoxycholate extract from matrix vesicles that included their phosphatase was studied under defined in vitro conditions. Electron microscopy showed that after removal of deoxycholate and lyophilization of the vesicle extract, new vesicles were reconstituted, often with multiple membrane layers. Both intact calf vesicles and reconstituted vesicles initiated Ca deposition maximally when supplied with ATP, GTP, CTP, or UTP. Only nucleoside triphosphates supported Ca deposition well; mono- and diphosphoesters, although hydrolyzed, were ineffective as substrates. Nucleoside triphosphates supported Ca deposition even if the final [Ca] X [P] reached in the reaction mixture was below a metastable level (3.5 mM2), suggesting that matrix vesicles or reconstituted vesicles promote calcification by localizing Ca or PO4 or both. ATP or GTP supported Ca deposition readily at concentrations ranging from 0.25 to 1.0 mM but, at 2.5 and 5.0 mM, Ca deposition was inhibited. The ATPase of intact matrix vesicles and reconstituted vesicles was stimulated by addition of Ca2+ and Mg2+. Ca deposition did not require additional Mg2+. These results lend support to the hypothesis that matrix vesicles and their phosphatases play an important role in mineralization.

Adenosine Triphosphatases↗
PubMed1979

Microscopic cytochemistry as matrix chemistry.

Microscopic cytochemical procedures, unlike reactions in test tubes, have to be undertaken while the compounds to be localized and quantified are present in the structural matrix of cells or tissues. Cytochemical reactions therefore differ from analogous staining reactions in homogeneous media because the diffusion of reagents into and out of the matrix and the molecular state around the compounds in the matrix to be stained, as well as the presence of many potentially interfering substances in the matrix, produce additional complications in terms of both specificity and quantitation. These complications can be studied quantitatively and in detail in artificially prepared matrices of defined geometry into which pure compounds or mixtures (of known composition) with other biological compounds can be incorporated. Since the composition of the matrix models is known, and the amount or activity of the compound to be stained can be analysed biochemically too, matrices are well suited to studies of the specificity of cytochemical reactions. They can also be used to study quantitative aspects of the influence of fixation procedures on the state of the incorporated compound. In addition, matrices can--by further biochemical analysis--be used to calibrate the intensity of cytophotometrically measured staining in terms of amounts of stained substance or in biochemical enzymic activity units. Finally, films and beads containing known amounts of known compounds can be used for objective quality control of commercially available cytochemical reagents.

Alkaline Phosphatase↗
PubMed1979

Long acting cAMP analogues enhance sulfate incorporation into matrix proteoglycans and suppress cell division of fetal rat chondrocytes in monolayer culture.

The relationship between replication and the synthesis of matrix sulfated proteoglycans was investigated with fetal rat chondrocytes grown in monolayer culture. The effect of N6 O2' dibutyryl adenosine 3', 5' cyclic monophosphate (DBcAMP), adenosine 3', 5' cyclic monophosphate (cAMP), 8 Bromo adenosine 3', 5' cyclic monophosphate (8 Br-cAMP), sodium butyrate and hydroxyurea was examined. Between 0.05 and 0.5 mM DBcAMP, a dose related inhibition of cell division and stimulation of [35SO=/4] incorporation into matrix proteoglycans was demonstrated. At the higher concentrations of DBcAMP, cell division was completely inhibited and the enhancement of [35SO=/4] incorporation into matrix proteoglycans ranged between 40 and 120% (P less than 0.01). Utilizing 14C-glucosamine and photometric determination of proteoglycans with Alcian Blue, it was demonstrated that the increase in sulfate incorporation reflected enhanced accumulation of extracellular matrix. The effects of DBcAMP were mimicked by 8 Br-cAMP, suggesting they were mediated by the adenylyl cyclase system. cAMP (0.05-0.5 mM), sodium butyrate (0.1-0.5 mM) and hydroxyurea (0.5-5 mM) partially or fully inhibited cell division, but either failed or only slightly enhanced sulfate incorporation. The enhanced sulfated proteoglycan deposition promoted by DBcAMP began 8 to 12 hours after serum stimulation, its onset occurred prior to thymidine incorporation and the effect persisted for 28 hours. Determination of cell volume demonstrated an increase in size of DBcAMP treated chondrocytes between 8 to 12 hours, coincident with the onset of increased sulfate incorporation. These results are consistent with a model where matrix sulfated proteoglycan deposition by chondrocytes is mediated by intracellular cAMP levels and occurs in the G1 phase of the cell cycle.

Animals↗
PubMed1977

Absence of mitochondrial terminal respiratory enzymes in cartilage matrix vesicles.

This study attempted to detect evidence of mitochondrial terminal respiratory components in matrix vesicles isolated from rachitic rat tibial epiphyseal plates. Biochemical assays for cytochrome c oxidase, NAD isocitrate dehydrogenase, NADP isocitrate dehydrogenase and succinate-cytochrome c reductase were negative. Polarimetric determinations revealed that the addition of succinate to matrix vesicles in suspension did not cause any increase in oxygen utilization. Spectrophotometric tracings of deoxycholate-solubilized matrix vesicles showed no characteristic absorption peaks or maxima belonging to any of the cytochrome complex components. Attempts to prepare pyridine hemochromes of cytochrome prosthetic groups from the matrix vesicles were also unsuccessful. The above results indicate that key components of mitochondrial respiratory systems are not detectable in rachitic matrix vesicles. The results are compatible with the interpretation that such vesicles are not derived from mitochondria.

Alkaline Phosphatase↗
PubMed1979

Incorporation of serum albumin into the developing dentine and enamel matrix in the rabbit incisor.

Rabbit serum albumin labeled with 125I was injected into rabbits (650-870 g). The incorporation pattern of the labeled albumin into the developing dentine and enamel matrix was studied 1 h, 6 h, and 3 days after the injection using autoradiography. Silver grains were observed over the predentine 1 h after the injection. They were found over the dentine matrix adjacent to the predentine-dentine junction at 6 h. The silver grain band was concentrated over the internal dentine matrix at 3 days. However, no appreciable amount of the silver grains could be seen over the enamel matrix at any time after the injection. It is possible that there might be some physiological barrier between the extravascular fluid and the enamel matrix. The role of the albumin in dentine is discussed.

Amelogenesis↗
PubMed1977

Characterization and serology of the matrix protein from a nuclear-polyhedrosis virus of Trichoplusia ni before and after degradation by an endogenous proteinase.

The intact matrix protein from a nuclear-polyhedrosis virus of the cabbage looper (Trichoplusia ni), isolated after inhibition of an endogenous serine-type proteinase, was further purified by molecular-sieve chromatography. The matrix protein was associated with carbohydrate moieties, and the carbohydrate content was determined for the two major peptides isolated after proteolysis by the endogenous proteinase. The association-dissociation interactions of the intact and proteinase-hydrolysed monomer units were characterized at high and low pH. At pH1.9, proteinase-degraded matrix protein dissociated into two different peptide fractions, FI and FII. Fraction FII, a single peptide of 9400 daltons, comprised one-third of the monomer unit of 28 000 daltons. At pH9.5, the degraded peptides were tightly associated in units equivalent to the intact monomer. These monomer equivalents associated to form a series of interconverting aggregates. The predominant aggregate sedimented at 11S and had a mol.wt greater than or equal to 200 000. Two non-cross-reacting antigens were present in the aggregate mixture. The presence of these two antigens does not reflect the presence of two different matrix proteins; rather, the expression of the antigens correlates with the degree of aggregation of the matrix protein.

Amino Acids↗
PubMed1978

Properties of matrix-bound dimer and monomer derivatives of immobilized creatine kinase from rabbit skeletal muscle.

Dimeric creatine kinase (EC 2.7.3.2) from rabbit skeletal muscle can be immobilized via a single subunit to CNBr-activated Sepharose 4B and subsequently treated with guanidine hydrochloride followed by renaturation to yield a catalytically active matrix-bound subunit derivative. The importance of the intact dimeric structure in the activation of the enzyme by acetate was demonstrated. Immobilization did not appear to alter the pH optimum of the enzyme, and the kinetic parameters fot the matrix-bound derivatives were generally similar to those for the soluble enzyme, but the matrix-bound derivatives showed higher thermal stability and greater resistance to denaturation than did the soluble enzyme. The rates of reaction of thiol groups of the matrix-bound derivatives with iodoacetamide in the absence and in the presence of combinations of substrates were similar to those of the soluble enzyme. Studies with 5,5'-dithiobis-(2-nitrobenzoic acid) and with iodoacetamide revealed the presence of an additional reactive thiol group in the matrix-bound subunit derivative, which is presumably masked in the dimeric derivatives.

Animals↗
PubMed1979

Isolation of the pericellular matrix of human fibroblast cultures.

The pericellular matrix of human fibroblast cultures was isolated, using sequential extraction with sodium deoxycholate and hypotonic buffer in the presence of protease inhibitor. The matrix attached to the growth substratum had a "sackcloth-like" structure as seen by phase contrast, immunofluorescence, and scanning electron microscopy, and it had a vaguely filamentous ultrastructure similar to that seen in intact cell layers. The matrix consisted of hyaluronic acid and heparan sulfate as the major glycosaminoglycan components and fibronectin and procollagen as major polypeptides as shown by metabolic labeling, gel electrophoresis, immunofluorescence, and collagenase digestion. This pericellular matrix can be regarded as an in vitro equivalent of the loose connective tissue matrix.

Cell Line↗
PubMed1979

Enamel matrix: structural proteins.

Cell-free, fetal bovine enamel tissue was examined intact by high resolution. 13C Fourier transform, nuclear magnetic resonance spectroscopy. Two types of protein chains were observed under these conditions, one exhibiting rapid mobility and accounting for approximately two-thirds of the enamel matrix, while the other exhibited restricted or anisotropic segmental motion and accounted for the remaining third of the matrix. Sequential extraction of this fetal enamel under non-degradative conditions with dissociative solvents yielded two biochemically distinct populations of matrix protein. As expected, the bulk of the matrix consisted of proline-rich amelogenins, although the SDS-gel electrophoresis molecular weights for these proteins were somewhat higher than those reported using other extraction methods. Approximately fifteen percent of the total matrix consisted of much higher molecular weight phosphoproteins (46,000-72,000 daltons) whose amino acid composition closely resembled that reported for mature enamel protein. These high molecular weight proteins were tightly bound to the fetal enamel apatite crystallites.

Animals↗
PubMed1979

The nature of covalent complexes of phosphoproteins with collagen in the bovine dentin matrix.

The bovine dentin matrix still contains some noncollagenous proteins after thorough extraction and decalcification. These have been obtained following digestion of the matrix by cyanogen bromide. Peptides containing non-collagenous portions were isolated by chromatography on diethylaminoethyl cellulose columns and fractionated on hydroxyapatite columns. Several fractions were obtained. The principal component was a complex between a highly-phosphorylated serine-aspartic acid-rich protein and a collagen peptide. These collagenous and non-collagenous moieties could not be separated from each other even under highly dissociative solvent conditions. After digestion with collagenase, the resulting phosphoprotein fraction still contained a few residues of hydroxyproline and hydroxylysine, and an enhanced content of proline, compared to the equivalent directly extractable phosphophoryn of the matrix. These data were interpreted as indicating that the phosphophoryn which is not extractable in 0.5M ethylenediaminetetraacetic acid is in fact covalently bound to some specific section of the matrix collagen. The covalent modification of the collagen matrix with highly acidic phosphoproteins may have an important role in the mineralization process.

Amino Acids↗
PubMed1979

Influence of magnesium depletion on matrix-induced endochondral bone formation.

The effect of magnesium deficiency on bone cell differentiation and bone formation was investigated using in vivo matrix-induced endochondral ossification as a test system. Demineralized bone matrix was implanted subcutaneously in young (35-day-old) male Long-Evans rats that had been fed a semisynthetic Mg-deficient diet (50 ppm Mg) for 7 days. Plasma Mg levels were reduced to 25-30% of control values at that time. Control rats were paired the same diet, supplemented to contain 1000 ppm Mg. The implants were harvested 7, 9, 11, 15, and 20 days after implantation and analyzed for Mg and Ca content, 45Ca incorporation, and alkaline phosphatase levels. At each stage, plaques (implants) removed from Mg-deficient rats showed retardation in cartilage and bone differentiation and matrix calcification. Magnesium content was markedly reduced when compared to the control plaques. Histological appearance of the matrix-induced plaques confirmed the retardation in bone development and mineralization suggested by the chemical indicators. Most marked was the virtual absence of bone marrow in 20-day-old plaques in Mg-depleted rats. These data show that bone cell differentiation can occur in a severely Mg-depleted environment, although the onset of mineralization and bone remodeling was delayed and bone marrow differentiation was impaired.

Alkaline Phosphatase↗
PubMedDate not supplied

Newer knowledge of skeletogenesis: macromolecular transitions in the extracellular matrix.

Morphogenesis of skeletal tissues is accompanied by dramatic changes in the types and amounts of extracellular macromolecules synthesized. These changes correlate with the morphological and structural characteristics of each tissue type involved in skeletogenesis, viz. mesenchyme, cartilage and bone. At the beginning of skeletogenesis, a hyaluronate-rich extracellular matrix may provide a beneficial milieu for mesenchymal cell migration and proliferation, and prevent precocious differentiation. This matrix also contains type I collagen and possibly a unique sulfated proteoglycan. Cartilage differentiation, during endochondral osteogenesis, involves the removal of hyaluronate and the production of large amounts of type II collagen and a characteristic chondroitin sulfate-proteoglycan. Further complex transitions in arrangement and concentration of proteoglycan occur in the epiphyseal growth plate followed by sudden depletion at the site of initiation of bone formation. In addition, at this site, the type of collagen synthesized reverts from type II back to type I. Bone formation at periosteal sites also involves removal of proteoglycan. The collagen component of both osteoid and bone matrix is type I but the level of hydroxylation of lysine moieties may be significantly higher in osteoid. It is proposed that changes in extracellular matrix composition are important factors in the control of morphogenesis as well as in providing suitable structural properties to the developing skeletal tissues.

Animals↗
PubMed1979

Effect of preimplantation treatment on the bone-forming potential of decalcified allogeneic and xenogeneic bone-matrix implants.

Bone-forming property of 0.6 M HCl decalcified (a) allogeneic bone matrix preserved in 70% alcohol, (b) allogeneic bone matrix preserved in anaesthetic ether, (c) allogeneic 'Ossein' provided by the Leather Research Institute, Madras, and (d) xenogeneic bone-matrix preserved in alcohol was studied by fitting the implants in surgically created complete circumferential osteo-periosteal gaps in the ulna of rabbits. Bone formation was assessed radiologically, macroscopically, histologically, and by tetracycline fluorescence up to 16 postimplantation weeks. Successful bridging of the gap by new bone formation was observed in 75% of (a) and 28.6% of (d) preserved up to 2 weeks. Ether-preserved implants did not induce bone formation. The 'Ossein' implants remained as inert material neither invaded by host cells nor inducing any bone formation. The xenogeneic implants exhibited local immune response which was probably responsible for poor osteogeneic response. Bone forming quality of bone-matrix implants appears to be influenced by the chemical treatment during preparation and preservation, host cellular response and immune reaction invoked by the implant.

Animals↗
PubMed1978

Effects of fluoride on in vitro calcification of tendon matrix.

Ca2+ and Pi uptake induced in vitro by a collagenous matrix derived from bovine tendon is inhibited by 1 X 10(-6) to 2 X 10(-5) M NaF and stimulated by 2 X 10(-5) to 2 X 10(-3) M NaF. Fluoride uptake occurs only over the latter concentration range. The uptake of Ca2+, Pi, and F-1 progresses toward a limiting extent at which the molar Ca/P and Ca/F values are 1.6 to 1.7 and 4.5 to 5.7, respectively. Although the matrix-bound mineral, previously formed in the absence of NaF, readily undergoes dissolution when exposed to a Ca2+- and P-free medium of pH less than 7.4, the bound mineral phase formed in the presence of NaF does not. We conclude that fluoroapatite is the primary matrix-bound mineral. The uptake of fluoride, Ca2+. amd Pi by both uncalcified and previously calcified matrices is inhibited by methylenediphosphonate and by phosphonoacetate as is calcification in the absence of NaF. Kinetic studies indicate that formation of a CaP complex precedes the uptake of F-1 and suggest that F-1 and OH-1 compete for interaction with that CaP complex during the calcification process. We concluded that fluoroapatite formation induced by the collagenous matrix occurs by a multistep pathway comparable to that proposed previously for hydroxyapatite formation.

Animals↗
PubMed1975

Characterization of developing antler cartilage matrix, II, An ultrastructural study.

Cartilage from the main beams and tines of deer antler was examined with the electron microscope. The material studied included prechondroblastic, chondroblastic and chondrocytic matrices. Exdysial microfibrils (5-10 nm in diameter) were observed in the matrix of the prechondroblastic zone. These microfibrils and associated amorphous material were continuous with electron-dense material that probably represented extracellular units of collagen polymers. Matrix (proteoglycan) granules were first observed in the chondroblastic zone. They stained positively with colloidal iron and therefore probably represented proteinpolysaccharides. The matrix granules of the chondroxytic (unmineralized and mineralized) zone were twice the diameter of those in the chondroblastic zone. Matrix vesicles were present in all three stages of development. They were in contact with cellular extensions and also arose directly from cell membranes in the immature zones. As in somatic mineralizing cartilage, these vesicles served as the foci for early mineralization. The initial mineralization process was associated with the membrane of the vesicles.

Animals↗
PubMed1979

Variant forms of matrix protein in Escherichia coli B/r bearing N plasmids.

Plasmids of the N incompatibility group have been found to decrease or virtually eliminate the synthesis of the 36,500 dalton outer membrane matrix protein of their Escherichia coli B/r hosts (Iyer, R. (1977) Biochim. Biophys. Acta 470, 258--272 and Iyer, R., Darby, V. and Holland, I.B. (1978) FEBS Lett. 85, 127--132) or modify its composition. Although the 34,000 dalton tol G protein is slightly increased in some strains, it is identical in composition to the homologous protein from the plasmidless host. In three of five N+ strains the synthesis of the modified matrix proteins depends on the temperature of cultivation of the strains in which they occur. The alterations to the matrix proteins are non-identical and do not affect the expression of several plasmid-coded functions including those of sensitivity to the N plasmid-specific filamentous bacteriophage IKe (Khatoon, H. and Iyer, R. (1971) Can. J. Microbiol. 17, 669--675), or their interbacterial transfer via conjugation to appropriate recipient strains. Thus, although the significance of the variant matrix proteins in N+ strains with respect to plasmid-mediated functions remains unclear, N plasmids nevertheless provide a convenient system which might be used to elucidate the events that precede the insertion of this protein into the outer membrane of E. coli B/r hosts.

Escherichia coli↗
PubMed1975

Studies on matrix vesicles isolated from chick epiphyseal cartilage. Association of pyrophosphatase and ATPase activities with alkaline phosphatase.

Fractions composed primarily of cells (Fraction I), membrane fragments (Fraction II) and matrix vesicles (Fraction III) were isolated from chick epiphyseal cartilage. The characteristics of the alkaline phosphatase (EC 3.1.3.1), pyrophosphatase (EC 3.6.1.1) and ATPase (EC 3.6.1.3) activities in the matrix vesicle fraction were studied in detail. Mg-2-+ was not absolutely essential to any of the activities, but at low levels was stimulatory in all cases. Higher concentrations inhibited both pyrophosphatase and ATPase activities. Both the stimulatory and inhibitory effects were pH-dependent. Ca-2-+ stimulated all activities weakly in the absence of Mg-2-+. However, when Mg-2-+ was present, Ca-2-+ was slightly inhibitory. Thus, none of the activities appear to have a requirement for Ca-2-+, and hence would not seem to be involved with active Ca-2-+ transport in the typical manner. The distribution of alkaline phosphatase, pyrophosphatase, and Mg-2-+ ATPase activities among the various cartilage fractions was identical, and concentrated primarily in the matrix vesicles. Conversely, the highest level of (Na-+ + K-+)-ATPase activity was found in the cell fraction. All activites showed nearly identical sensitivities to levamisole (4 - 10-3 M) which caused nearly complete inhibition of alkaline phosphatase and pyrophosphatase. About 10-15% of the ATPase activity was levamisole-insensitive. The data are consistent with the concept that the Mg-2-+-ATPase and pyrophosphatase activities of matrix vesicles stem from one enzyme, namely, alkaline phosphatase.

Adenosine Triphosphatases↗