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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↗
PubMed1978

Scanning electron microscopy studies on the origin and structure of matrix vesicles in epiphyseal cartilage from young rats.

Epiphyseal plates of young rats were examined by scanning electron microscopy to study the distribution, morphology and origin or the matrix vesicles (calcifying globules) and the results were compared with the findings on transmission electron microscopy. The matrix vesicles, 0.1 micrometer in diameter, were found to cover the intercolumnar septa and to increase gradually in number from the zone of proliferation to the zone of provisional calcification. In the intercolumnar septa of hypertrophic and calcifying cartilage, the vesicles aggregated to form calcospherites, i.e. mineralized globules about 1 micrometer in diameter. Chondrocytes showed numerous cell processes that were longer and more abundant in the more mature cells. In the zone of maturation many processes had enlarged tips with small globular projections ("bulges"), about 0.1 micrometer in diameter, which resembled the matrix vesicles covering chondrocytic lacunae. In the zones of hypertrophy and provisional calcification, many of these bulges aggregated to form larger, spherical structures. It is suggested that matrix vesicles in cartilage originate by budding from cell processess, and that in the zone of provisional calcification they aggregate to form the calcospherites, which are the loci of initial calcification of cartilage.

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

A macromolecular inhibitor of in vitro calcification of tendon matrix.

Bovine and human tendon tissue do not induce calcification in vitro. However, extraction of those tissues with 3% Na2HPO4 converts them to calcifiable matrices. The supernatant fraction derived from the extraction contains a nondialyzable, perchloric acid soluble component that inhibits calcification of the extracted matrix. This inhibitory substance is characterized by a molecular weight in the range of 85,000-100,000. Exposure to pronase or hyaluronidase did not alter the inhibitory potency but did render the inhibitor dialyzable. Commercial sources of hyaluronic acid, chondrotitin-6-sulfate, chrondroitin-4-sulfate, dermatan sulfate, heparin and lysozyme did not inhibit calcification of the extracted matrix. Phosvitin, a phosphoglycoprotein is a potent inhibitor. Although phosvitin and the tendon extract also inhibit calcification of previously calcified matrix, they have no detectable effect on the rate of decalcification. We conclude that the mechanism of inhibition is characterized by a degree of specificity and that phosvitin and a macromolecular component of tendon tissue blocks conversion of an intermediate matrix-bound CaP complex to crystalline apatite. It seems reasonable that the tendon inhibitor could function in situ and possibly in vivo to control calcification of tendon tissue.

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↗
PubMed1977

Properties of trout hemoglobin covalently bound to a solid matrix.

This paper reports the ligand binding properties of the major hemoglobin component from trout (Salmo irideus) covalently bound to a solid matrix (Sepharose or Sephadex). A comparison between the functional properties of this protein in solution and of the protein-matrix complex shows significant changes although the basic properties of the molecule are maintained on covalent binding to Sepharose (or Sephadex). Thus the Root effect, characteristic of Hb trout IV, is still present while the heme-heme interactions are, on the average, smaller in the matrix bound protein as compared to the soluble form. No differences in the O2 binding properties were observed when the protein was coupled to the resin, as the ligand bound or as the ligand free derivative. Although an unequivocal interpretation of the data is made difficult by the lack of information on the number and identity of the groups involved in the coupling, the main changes in the protein functional properties may be related to the chemical modifications "per se" more than to the immobilization imposed to the macromolecule by coupling to the matrix. Structural changes which mainly involve perturbation of the tertiary structure of the molecule may qualitatively rationalize the data.

Animals↗
PubMed1979

In vitro binding of protoheme IX and protoporphyrin IX to components in the matrix of rat liver mitochondria.

The matrix fraction of rat liver mitochondria contains several components capable of binding protoheme IX and protoporphyrin IX in vitro. When binding is analyzed by sucrose density gradient centrifugation, two main groups of components can be separated; i.e. one of high and one of low molecular weight. Experimental evidence is presented indicating a protein nature of these components, and at least six species were detected by gel electrophoresis. The binding of protoheme IX and protoporphyrin IX to matrix components is also evident from a marked change in the heme and porphyrin absorbance spectra in the presence of added matrix. The data obtained indicate that the matrix fraction has a high total binding capacity for heme, but the affinity for heme of the various components seems to be different. Based on the separation of bound and free heme by gel electrophoresis it is concluded that the heme-binding capacity of the high affinity components does not exceed 14 nmol heme . mg-1 protein.

Animals↗
PubMed2026

Tissue-derived extracellular matrix hydrogels instruct epigenetic adaptation in metastatic colonization.

The extracellular matrix (ECM) plays a central role in regulating tumor progression and metastatic colonization by providing biochemical and mechanical signals that shape cancer cell fate. However, most organoid culture systems rely on basement membrane extracts that fail to reproduce the tissue-specific extracellular environments encountered during metastasis. Here, we develop tissue-derived decellularized matrix hydrogels to reconstruct organ-specific microenvironments and investigate epigenetic adaptation to ECM cues during metastatic colonization. Patient-derived colorectal cancer organoids cultured in colon-derived matrices exhibited enhanced maintenance of stem-like phenotypes and colon-specific chromatin accessibility landscapes compared with cultures grown in basement membrane extracts, demonstrating improved physiological relevance for primary tumor modeling. When exposed to matrices derived from secondary organs, the organoids showed distinct growth phenotypes accompanied by rapid, tissue-dependent chromatin accessibility remodeling, indicating that ECM composition alone can reshape regulatory programs governing metastatic adaptation. Notably, liver-derived matrices selectively activated hepatocyte nuclear factor 4 alpha (HNF4A)-associated transcriptional networks and created a context-specific dependence on c-MET signaling for survival. Functional perturbation of HNF4A or c-MET signaling confirmed that both are required for organoid formation specifically within the liver matrix environment. Together, these findings establish tissue-derived matrix hydrogels as instructive bioactive materials that actively regulate cancer cell epigenetic states and reveal microenvironment-specific therapeutic vulnerabilities during early metastatic colonization.

Journal Article↗
PubMed1978

Phosphorylation of adenosine monophosphate in the mitochondrial matrix.

The origin of the GTP needed for th phosphorylation of AMP in the mitochondrial matrix was investigated. When short-chain fatty acids are metabolized by hepatocytes, AMP is readily formed within the matrix by the butyryl-CoA ligase (AMP-forming) reaction (EC 6.2.1.2). The rate of matrix AMP formation in rat hepatocytes was calculated from the rate of ketone-body formation. The rate of the reconversion of matrix AMP into ADP by GTP-AMP transphosphorylase is limited by the rate of supply of GTP. GTP can be formed either by succinic thiokinase (EC 6.2.1.4) or by nucleoside diphosphokinase (EC 2.7.4.6). The rate of the succinic thiokinase reaction was calculated from turnover of the tricarboxylic acid cycle and this was calculated from the rate of O2 consumption and ketone-body formation. The results show that nucleoside diphosphokinase can make a major contribution (up to 80%) to the supply of GTP under the test conditions.

Adenosine Monophosphate↗
PubMed1979

Experiments with the longterm rumen simulation technique (Rusitec); use of soluble food and an inert solid matrix.

1. The role of soluble nutrients and of the solid matrix in rumen fermentation was investigated in some detail, and experiments designed to explore the possibility of using a balanced soluble diet and an inert solid matrix, are described. 2. The use of a balanced soluble substrate as the only source of nutrients in the presence of an inert solid phase in the reaction vessels results in vigorous fermentation but is accompanied by disappearance of protozoa from the effluent. 3. In the absence of digestible solid phase, the rate of fermentation and the fermentation pattern depends mainly on the amount and type of nutrients supplied and to a smaller extent on the dilution rate, the variations being greatest at low dilution rates. 4. The solid matrix in the form of wood shavings or the residue remaining after prolonged digestion of hay could sequestrate micro-organisms and could be used as solid phase, but the defined mixture of soluble substrates used resulted in somewhat abnormal fermentation compared with fermentation obtained with solid food. 5. When the solid food included some hay extract and when the dilution rate was not too great a reduced output of protozoa could be maintained. At high dilution rate the outflow of protozoa was negligible and yet considerable numbers of protozoa were found in the solid matrix and associated liquid. 6. A three-compartment model was developed to describe the flow of liquid and microbial matter within the simplified system.

Animal Feed↗
PubMed1977

Immunologic recognition of influenza virus-infected cells. II. Expression of influenza A matrix protein on the infected cell surface and its role in recognition by cross-reactive cytotoxic T cells.

Two distinct subpopulations of cytotoxic T cells are generated in the primary or secondary response of mice to type A influenza viruses. One subpopulation is specific for the immunizing virus strain. The other subpopulation shows a high degree of cross-reactivity for heterologous type A virus of a different subtype. This report examines the possibility that distinct influenza virus antigens, expressed on the surface of the infected cell, are recognized by the different subpopulations of influenza-specific cytotoxic T cells. Data are presented which demonstrate that influenza A matrix protein, an internal virion antigen, is detectable on the surface of target cells infected with influenza A viruses of different subtypes. Since this viral antigen is type specific, i.e., serologically cross-reactive among all type A influenza viruses, it could serve as the target for cross-reactive cytotoxic T cells. To further examine the specificity of the two cytotoxic T-cell subpopulations, experiments were carried out by using the inhibitor of glycoprotein synthesis - 2-Deoxy-D-Glucose 2-DG. These experiments examine first the effect of 2-DG on the expression of influenza matrix protein and viral glycoprotein on the infected cell surface and second, the susceptibility of 2-DG-treated target cells to lysis by cytotoxic T cells. 2-DG inhibits the expression of the viral hemagglutinin glycoprotein on the cell surface but does not inhibit the expression of the nonglycosylated matrix protein. Furthermore, inhibition of glycoprotein synthesis in infected target cells abrogates the reactivity of infected target cells to lysis by virus strain-specific but not cross- reactive cytotoxic T cells. These findings suggest that the influenza glycoproteins (hemagglutinin and/or neuraminidase) and the nonglycosylated matrix protein are the targets for the virus strain- specific and cross-reactive cytotoxic T cells, respectively. These results are discussed in the light of available information on influenza virus structure and the biology of influenza infection and in terms of current models for cytotoxic T-cell recognition of virus-infected cells.

Antibodies, Viral↗
PubMed1978

Simian virus 40 (SV40)-specific proteins associated with the nuclear matrix isolated from adenovirus type 2-SV40 hybrid virus-infected HeLa cells carry SV40 U-antigen determinants.

The distribution of simian virus 40 (SV40)-specific proteins in nuclear subfractions of pulse-chase-labeled HeLa cells infected with nondefective adenovirus type 2 (Ad2)-SV40 hybrid viruses was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND5 specifically associate with the nuclear matrix and are virtually absent from the high-salt nuclear extract. In Ad2+ND4-infected HeLa cells, the SV40-specific proteins with molecular weights of 64,000 (64K) and lower also specifically associate with the nuclear matrix. The SV40-specific 72K, 74K, and 95K proteins were found both in the nuclear matrix and in the high-salt nuclear extract. Analyses of the nuclear matrices isolated from hybrid virus-infected cells by immunofluorescence microscopy showed that SV40 U-antigen-positive sera from SV40 tumor-bearing hamsters react with SV40-specific proteins integrated into nuclear matrices of HeLa cells infected by Ad2+ND1, Ad2+ND2, and Ad2+ND4, but not with nuclear matrices of HeLa cells infected by Ad2+ND5. This suggests that SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND4 integrated into the nuclear matrix carry SV40 U-antigen determinants. The apparent discrepancy in the subcellular localization of SV40-specific proteins in hybrid virus-infected cells when analyzed by biochemical cell fractionation procedures and when analyzed by immunofluorescence staining is discussed.

Adenoviruses, Human↗
PubMed1976

Age dependence of the biosynthesis of intercellular matrix macromolecules of rabbit aorta in organ culture and cell culture.

The age dependence of the relative rate of biosynthesis of intercellular matrix macromolecules was studied in organ culture and cell culture obtained from aortas of newborn, young and adult rabbits. In organ culture there was a strong decrease with age of the rate of incorporation of (14C)-lysine and (3H)-glucosamine in all macromolecular fractions. Neosynthesis of elastin could be demonstrated by the isolation of labelled demosine at all ages. In cell cultures derived from newborn and adult aortas, no decrease in total incorporation was noticed. The pattern of synthesis and secretion of glycosaminoglycans and glycoproteins did however change with age. These results suggest the existence of matrix-dependent and of a matrix-independent regulation of the relative rate of synthesis of matrix macromolecules.

Aging↗
PubMed1976

The role of the matrix substance in formation of urinary stones.

This study deals with the role of the stone matrix substance in formation of urinary stones. A series of coagulation experiments were conducted by determining the sedimentation rate of calcium carbonate suspension with respect to the following substances: sodium alginate, stone matrix substance, bovine albumin and chondroitin sulfate C, these were each added to a separate fine particle suspension of calcium carbonate. Changes in zeta-potential of the suspension particles after addition of the above materials were determined microscopically using Usui's method. The results obtained in this study indicate that sodium alginate, the matrix substance, bovine albumin and chondroitin sulfate C act on the suspension particles, and as a result, coagulation is produced by a decrease of the zeta-potential of the particles. Application of kinetic energy to the coagulate caused by sodium alginate resulted in the formation of a solid. From these results it is considered that the matrix substance is not incorporated by accident in urinary stones, but it participates in the formation of them.

Adolescent↗