Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Matrix”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed1993

Modulation of procoagulant activity of extracellular endothelial matrix by anti-tissue factor antibody and the synthetic peptide Arg-Gly-Asp-Val. Experiments with flowing non-anticoagulated human blood.

Fibrin forms on and binds to the extracellular matrix of endotoxin-stimulated endothelium when exposed to flowing non-anticoagulated blood. These processes have been investigated by employing a human ex vivo perfusion model, a synthetic peptide Arg-Gly-Asp-Val and a monoclonal anti-tissue factor antibody which inhibits tissue factor/FVIIa-induced coagulation. Procoagulant extracellular matrix on plastic cover-slips was prepared from cultures of endotoxin-stimulated human endothelium following brief exposure to 0.1 M NH4OH. Non-anticoagulated blood was drawn directly from an antecubital vein by a pump at venous (100/s) and arterial (650/s) wall shear rates over the matrix-coated cover-slips positioned in parallel-plate perfusion chambers. Deposition of fibrin and platelets on the matrix was quantified by morphometry. Preincubation of the matrix with Arg-Gly-Asp-Val inhibited fibrin deposition by 80-90% at both venous (P < 0.001) and arterial shear (P < 0.05). However, the peptide had no effect on the clotting time in a modified one-stage clotting assay where coagulation was initiated by lysed endotoxin-stimulated endothelial cells, indicating that the peptide interfered with the binding of fibrin to the matrix in the perfusion model. Preincubation of the matrix with the anti-tissue factor antibody, which blocked the coagulant activity ( > 95%, P < 0.01) in the modified coagulation assay, also inhibited fibrin deposition on the matrix by 90-95% (P < 0.01) at both shear rates. In the absence of either inhibitor, platelets adhered preferentially to the fibrin meshwork, and more so at arterial shear. Platelet thrombus formation on the fibrin coat was in particular pronounced at arterial shear. Thus, it appears that the extracellular matrix of endotoxin-stimulated endothelium initiates coagulation predominantly through tissue factor/FVIIa and that the resulting fibrin meshwork forming on the surface induces rapid platelet thrombus formation. The inhibitory effect of Arg-Gly-Asp-Val on the binding of fibrin to the matrix may indicate the presence of specific matrix fibrinogen/fibrin binding site(s) with a recognition sequence of Arg-Gly-Asp.

Amino Acid Sequence↗
PubMed1988

Ultrastructure of odontogenic cells during enameloid matrix synthesis in tooth buds from an elasmobranch, Raja erinacae.

The ultrastructure of the inner dental epithelial cells (IDE) and odontoblasts in elasmobranch (Raja erinacae) tooth buds was investigated by transmission electron microscopy to determine what contribution each cell type makes to the forming enameloid matrix. Row II, early stage, IDE cells contained few organelles associated with protein synthesis, whereas preodontoblasts appeared competent to initiate extracellular matrix production. Row III IDE cells are also devoid of organelles related to secretory protein synthesis, although these IDE cells accumulated large pools of intracellular glycogen. The glycogen appeared to be packaged into vesicles and exocytosed into the lateral extracellular space toward the forming enameloid matrix. Row III odontoblasts had a morphology consistent with an active protein secretory cell. No procollagen granules were present within the odontoblasts, however, nor were many collagen fibers observed in the enameloid matrix. Instead, non-collagenous "giant" fibers having 17.5-nm periodic cross striations were associated with the invaginations of odontoblast cell processes. Giant fibers, which spanned a clear zone adjacent to the odontoblasts, terminated within the enameloid matrix. Smaller 25-nm-wide "unit" fibers emanated from the giant fiber tips to form the bulk of the enameloid matrix. The clear zone, which separated the odontoblasts from the enameloid matrix at early stages, diminished in size at later stages until the odontoblast processes were completely embedded in the enameloid matrix. Nascent enameloid crystallites were observed only after a layer of unmineralized predentin was deposited beneath fully formed enameloid matrix. The results suggest that the major constituent of the enameloid matrix in skates is a non-collagenous protein derived from the odontoblasts. The inner dental epithelial cells appear to contribute large quantities of carbohydrates to the forming enameloid matrix.

Animals↗
PubMed2000

The influence of corneal stromal matrix proteins on the migration of human corneal fibroblasts.

Motivated by the alterations seen in the corneal matrix composition after photorefractive keratectomy and the migration of corneal keratocytes seen following this procedure, the locomotor response of corneal stromal fibroblasts to various extracellular matrix proteins was determined. In addition, the involvement of integrin mediated attachment to the matrix proteins was investigated. Quantitative invasion assays were performed using collagen gels, supplemented with either fibronectin, tenascin, collagen type V, collagen type VI, chondroitin sulfate or keratan sulfate. The ultrastructure of the gels was visualized by scanning electron microscopy and related to the migration results. The extent of alpha(1)beta(1), alpha(2)beta(1), alpha(3)beta(1)and alpha(5)beta(1)integrin mediated attachment to the matrix proteins was evaluated using blocking antibodies. Fibronectin increased corneal fibroblast migration significantly, and served as an excellent substrate for cellular attachment, mediated by the alpha(5)beta(1)integrin. Addition of tenascin to the fibronectin-containing gels disrupted these effects, while attachment to this matrix also involved the integrins alpha(2)beta(1)and alpha(3)beta(1). Chondroitin sulfate and collagen types V and VI primarily altered the structure of the collagen matrix, resulting in an inhibition of migration by the collagens and an increase by chondroitin sulfate. They all served as poor substrates for attachment. Thus, the migratory activity of corneal fibroblasts in vitro is influenced by the composition of the surrounding extracellular matrix, either by integrin mediated cell-matrix interactions or through matrix-matrix interactions. This study provides evidence that the provisional matrix deposited in a corneal stromal wound may facilitate the entry of migrating corneal fibroblasts.

Antibodies, Blocking↗
PubMed1988

Association of Autographa californica nuclear polyhedrosis virus (AcMNPV) with the nuclear matrix.

Nuclear matrices from uninfected Spodoptera frugiperda cells and those infected with Autographa californica nuclear polyhedrosis virus (AcMNPV) were isolated and their protein constituents were compared. Proteins were characterized according to size and several different antibodies to Drosophila nuclear proteins were employed in an attempt to identify the proteins comprising this nuclear substructure. Three species of lamins were identified as major constituents of the nuclear matrix of Spodoptera cells. Two DNA-binding proteins having molecular weights of 54 and 36 kDa were also identified as components of the nuclear matrix of uninfected cells. Infection resulted in a superimposition of viral proteins upon the nuclear matrix of the host cell. Polyhedrin, the basic viral DNA-binding protein (p6.9), and the major capsid protein of AcMNPV were identified immunologically as components of the nuclear matrix fraction of infected cells. Infection also resulted in the increased association of cellular histones with the nuclear matrix. DNA-binding assays demonstrated histones and p6.9 were the predominant DNA-binding proteins associated with the nuclear matrix of infected cells. Nuclear matrices from uninfected cells and cells infected with AcMNPV for 10 and 24 hr were examined using transmission electron microscopy. Morphologically, the nuclear matrix of the uninfected cell consists of the outer nuclear lamina (including nuclear pore complexes), an internal fibrogranular protein constituent, and a residual nucleolar structure. Numerous viral capsids were observed associated with the nuclear matrix in cells infected with either wild-type AcMNPV or a polyhedrin-deletion mutant by 10 hr p.i. The capsids appeared to be attached in an end-on association with the internal fibrogranular protein network of the nuclear matrix. The matrix-associated capsids were similar in width and length to those packaged within the polyhedra. In addition to the capsids, polyhedra in various stages of maturation were seen at 24 hr following infection of the cells with the wild-type virus. The nuclear matrix of the infected cell appears to play an important role in baculovirus assembly.

Animals↗
PubMed2001

Stable reformulation of transfer matrix method for wave propagation in layered anisotropic media.

The numerical instability problem in the standard transfer matrix method has been resolved by introducing the layer stiffness matrix and using an efficient recursive algorithm to calculate the global stiffness matrix for an arbitrary anisotropic layered structure. For general anisotropy the computational algorithm is formulated in matrix form. In the plane of symmetry of an orthotropic layer the layer stiffness matrix is represented analytically. It is shown that the elements of the stiffness matrix are as simple as those of the transfer matrix and only six of them are independent. Reflection and transmission coefficients for layered media bounded by liquid or solid semi-spaces are formulated as functions of the total stiffness matrix elements. It has been demonstrated that this algorithm is unconditionally stable and more efficient than the standard transfer matrix method. The stiffness matrix formulation is convenient in satisfying boundary conditions for different layered media cases and in obtaining modal solutions. Based on this method characteristic equations for Lamb and surface waves in multilayered orthotropic media have been obtained. Due to the stability of the stiffness matrix method, the solutions of the characteristic equations are numerically stable and efficient. Numerical examples are given.

Algorithms↗
PubMed1996

Histologic and immunohistochemical features in biopsy sites in which bovine collagen matrix was used for hemostasis.

BACKGROUND: Bovine collagen matrix (Helistat and Helatene), which is used primarily for hemostasis, decreases wound contracture in skin biopsy sites and promotes wound granulation. OBJECTIVE: Our purpose was to evaluate excision specimens of previous biopsy sites to determine whether there are histologic differences between cases in which bovine collagen matrix was used for hemostasis and those in which it was not used. METHODS: Thirty-two diagnostic punch biopsies were done with hemostasis obtained with bovine collagen matrix in 24 biopsies and by pressure alone in eight. The biopsy sites were reexcised at various time intervals, and the histologic and immunohistochemical features were evaluated and compared. RESULTS: In specimens in which collagen matrix was used, migration of stromal and epithelial cells along the bovine collagen matrix was evident by 2 days and had progressed rapidly by 4 days. Around and within the matrix hyaluronic acid increased during the first 8 to 10 days. Initially stromal cells stained with CD34 and reticulum fibers were present at 8 to 10 days. AT 12 to 15 days, factor XIIIa+ stromal cells were present within the matrix, and host collagen fibers were present and well-oriented within the degenerating matrix. Biopsy specimens allowed to heal without the matrix showed a delayed and an uneven increase in hyaluronic acid. Furthermore, the granulation tissue within the dermis showed no organization with a persistent acute inflammatory infiltrate and increased muscle actin-positive stromal cells as scar formation proceeded. CONCLUSION: Bovine collagen products appear to provide a matrix that promotes thrombosis. The collagen matrix also promotes migration and attachment of stomal and epithelial cells, thereby organizing and accelerating wound healing.

Actins↗
PubMed1982

Ribonucleic acid precursors are associated with the chick oviduct nuclear matrix.

Nuclear matrix was prepared by sequential treatment of oviduct nuclei with Triton X-100, DNase I, and 2 M NaCl. Published procedures were modified such that as many steps as possible were performed at -20 degrees C to minimize endogenous ribonuclease activity. Examination of electron micrographs confirmed the isolation of intact nuclear matrix structures. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins in these structures showed an absence of histones and an enrichment of certain nonhistone proteins. RNA was isolated from the nuclear matrix preparations and subjected to denaturing gel electrophoresis. Gels were analyzed by ethidium bromide staining and by hybridization of Northern blots to cloned DNA probes for ovalbumin, ovomucoid, 5.8S ribosomal RNA, and U1 RNA. All of the precursors to ovalbumin and ovomucoid mRNAs (including various splicing intermediates) and all of the precursors to ribosomal RNA were associated exclusively with the nuclear matrix fraction. By contrast, mature ovalbumin and ovomucoid mRNAs were distributed between matrix and nonmatrix fractions. These observations were further supported by quantitative hybridization analysis of the RNA in nuclear and matrix fractions. It was found that less than 50% of the mature message of intact nuclei was recovered in the matrix, while most significantly, over 95% of the mRNA precursors remained associated with the matrix. Finally, mature ribosomal RNAs and virtually all of the small nuclear RNAs (including U1 RNA) were also distributed between matrix and nonmatrix fractions. Our results suggest that all precursor RNAs (be they precursors to mRNA or rRNA) are exclusively associated with the nuclear matrix and support the notion that the nuclear matrix may be the structural site for RNA processing within the nuclei of eucaryotic cells.

Animals↗
PubMed2006

Expression of Smad1 is directly associated with mesangial matrix expansion in rat diabetic nephropathy.

Diabetic nephropathy is the leading cause of end-stage renal disease, and glomerular mesangial matrix expansion is the hallmark in diabetic nephropathy. However, the precise mechanism for the development of mesangial matrix expansion has remained unknown. The key component involved in mesangial matrix expansion is type IV collagen (Col4). Recently, we have reported that Smad1 transcriptionally regulates expression of Col4 under diabetic conditions in vitro. Here we show that this direct regulator of Col4 also plays a crucial role for mesangial matrix expansion in vivo. Streptozotocin-induced diabetic rats are the model of incipient diabetic nephropathy, and showed various levels of mesangial matrix expansion at 24 weeks. The glomerular expression of Smad1 was significantly increased in diabetic rats with more mesangial matrix expansion by Western blot and immunohistochemical analysis. Furthermore, the glomerular expression of Smad1 was closely correlated with the glomerular expression of Col4 and smooth muscle alpha actin (alpha-SMA), while albuminuria or glomerular filtration rate was not correlated with mesangial matrix expansion. We also found that urinary excretion of Smad1 was closely associated with the severity of mesangial matrix expansion. In cultured mesangial cells expression of Smad1 upregulated the transcriptional activity of key molecules in mesangial matrix expansion, such as Col4 and alpha-SMA. These data indicate the critical involvement of Smad1 in mesangial matrix expansion in the early phase of diabetic nephropathy. Our data imply that urinary Smad1 might be a representative diagnostic marker for mesangial matrix expansion in diabetic nephropathy.

Actins↗
PubMed1983

Modulation of collagen synthesis by a growth factor and by the extracellular matrix: comparison of cellular response to two different stimuli.

Cultured bovine corneal endothelial cells can be grown in three ways: on plastic, on plastic with fibroblast growth factor present in the media, and on their own preformed extracellular matrix. On plastic alone, cells grow in a disorderly fashion and secrete matrix on all cell surfaces. Cells grown on plastic with growth factor or on a matrix, at confluence, have matrix deposition only on the basal surface of the cells and an orderly contact-inhibited pattern of growth. This correlates with the polarity they demonstrate histologically. This cell-matrix pattern resembles the pattern observed in vivo. Both the soluble growth factor and the extracellular matrix are able to modulate the pattern of collagen synthesis and deposition by cells, but they do so in two entirely different ways. In cells grown on the extracellular matrix, total collagen synthesis is lower but more efficient. Collagen is deposited primarily into the cell layer even at the early sparse stage of culture. In cells grown on plastic with growth factor in the media, collagen is initially secreted into the media and does not become incorporated into the matrix. The deposition of collagen on the basal surface of cell occurs only late in the culture, and is achieved by increments in a stepwise manner. The in vivo-like pattern is not manifest until confluence has been reached. Thus, the extracellular matrix functions not only as a structural support, but is also instructional to the cells plated on it. In this case, the matrix regulates the level of collagen synthesis in the cells and modulates the pattern of collagen deposition. Soluble growth factors may act in part by enhancing a cell's ability to elaborate an appropriate matrix pattern necessary for the cell's own growth and accurate function.

Animals↗
PubMed1990

Regulation of acrosomal matrix dispersion in digitonin-permeabilized guinea pig spermatozoa.

Digitonin-permeabilized guinea pig spermatozoa undergo acrosomal matrix dispersion in response to 2.0 mM CaCl2. In this report, the effects of pH and metal ions on matrix dispersion in permeabilized spermatozoa are examined. Calcium-induced dispersion of the acrosomal matrix was dependent on the calcium concentration; the response was not observed at concentrations of CaCl2 less than 50 microM. Magnesium could not substitute for calcium and, in fact, had a retarding effect on the calcium-induced response. Matrix dispersion was also found to be pH-dependent. The induction of matrix dispersion was inhibited at pH 5.6 and pH 9.5 relative to the responses observed at pH 6.3 and pH 7.8. Nigericin induced acrosomal matrix dispersion in the absence of added calcium, indicating a possible role of Na+/H+ exchange across the outer acrosomal membrane in initiating the matrix modification. Sodium was required for the action of nigericin; the ionophore was ineffective in medium in which choline chloride or sucrose was substituted for NaCl. In contrast, the calcium-induced dispersion of the acrosomal matrix occurred in the absence of sodium. Furthermore, low concentrations of calcium inhibited an adenosine triphosphatase activity associated with isolated acrosomal apical segments. These data are consistent with the hypothesis that calcium induces alkalinization of the acrosome, leading to matrix dispersion. However, permeabilized spermatozoa incubated at either pH 9.5 or in the presence of 50 mM NH4Cl at pH 7.5 failed to undergo spontaneous matrix dispersion, suggesting that elevated intraacrosomal pH alone was not sufficient to initiate the reaction. The proposed alternative hypothesis is that calcium initiates matrix dispersion by a mechanism in which elevated intraacrosomal pH may be a secondary response.

Acrosome↗
PubMed2004

Evolution and stability of the G-matrix on a landscape with a moving optimum.

In quantitative genetics, the genetic architecture of traits, described in terms of variances and covariances, plays a major role in determining the trajectory of evolutionary change. Hence, the genetic variance-covariance matrix (G-matrix) is a critical component of modern quantitative genetics theory. Considerable debate has surrounded the issue of G-matrix constancy because unstable G-matrices provide major difficulties for evolutionary inference. Empirical studies and analytical theory have not resolved the debate. Here we present the results of stochastic models of G-matrix evolution in a population responding to an adaptive landscape with an optimum that moves at a constant rate. This study builds on the previous results of stochastic simulations of G-matrix stability under stabilizing selection arising from a stationary optimum. The addition of a moving optimum leads to several important new insights. First, evolution along genetic lines of least resistance increases stability of the orientation of the G-matrix relative to stabilizing selection alone. Evolution across genetic lines of least resistance decreases G-matrix stability. Second, evolution in response to a continuously changing optimum can produce persistent maladaptation for a correlated trait, even if its optimum does not change. Third, the retrospective analysis of selection performs very well when the mean G-matrix (G) is known with certainty, indicating that covariance between G and the directional selection gradient beta is usually small enough in magnitude that it introduces only a small bias in estimates of the net selection gradient. Our results also show, however, that the contemporary G-matrix only serves as a rough guide to G. The most promising approach for the estimation of G is probably through comparative phylogenetic analysis. Overall, our results show that directional selection actually can increase stability of the G-matrix and that retrospective analysis of selection is inherently feasible. One major remaining challenge is to gain a sufficient understanding of the G-matrix to allow the confident estimation of G.

Adaptation, Biological↗
PubMed1995

Pattern formation in the mammalian forebrain: striatal patch and matrix neurons intermix prior to compartment formation.

The striatum of the mammalian forebrain is divided into two compartments: the patches and the matrix. Neurons of the patch compartment in the rat striatum become postmitotic earlier in neurogenesis than neurons of the matrix compartment. The selective adhesion of patch neurons to one another has been suggested previously to be an important developmental mechanism of striatal compartmentation. We asked if the selective adhesion of patch neurons is expressed before or after the migration of the majority of the matrix neurons into the striatum. Patch neurons were labelled in vivo by a fluorescent retrograde tracer injected into the substantia nigra on embryonic day 19, which almost exclusively labelled patch neurons. Matrix neurons were labelled with a maternal injection of bromodeoxyuridine at embryonic day 18. When animals were killed at embryonic day 20, the majority of the retrogradely labelled patch neurons were intermixed with the bromodeoxyuridine-labelled matrix neurons, although there appeared to be clustering of some of the patch neurons. However, by postnatal day 2 there was a complete segregation of the clusters of the retrogradely labelled patch neurons from the bromodeoxyuridine-labelled matrix neurons in the striatum. This process was modelled in vitro. The patch and matrix compartments were labelled in vivo at embryonic day 13 and 18 respectively, with different birthdate markers ([3H]thymidine or bromodeoxyuridine). At embryonic day 20 the striatal tissue was removed, dissociated and reaggregated in suspension cultures. After 1 day in vitro, labelled patch and matrix neurons were randomly intermixed within the reaggregates. Examination of the cultures at 2.5 and 4 days in vitro revealed clumping of the labelled patch neurons towards the centres of the reaggregates. Over this same period, the labelled matrix neurons did not clump and were dispersed towards the periphery of the reaggregates. The results suggest that patch neuron adhesiveness may appear relatively soon after these neurons become postmitotic, but that this adhesiveness is unable to overcome the initial force produced by the massive migration of matrix neurons into the striatum. We hypothesize that a migratory phase of embryonic striatal development exists, when fated patch and matrix neurons intermix. After this migratory phase, patch neuron adhesiveness can produce the mature segregation of the striatal compartments.

Aging↗
PubMed2006

Hybrid compliance-stiffness matrix method for stable analysis of elastic wave propagation in multilayered anisotropic media.

This paper presents the hybrid compliance-stiffness matrix method for stable analysis of elastic wave propagation in multilayered anisotropic media. The method utilizes the hybrid matrix of each layer in a recursive algorithm to deduce the stack hybrid matrix for a multilayered structure. Like the stiffness matrix method, the hybrid matrix method is able to eliminate the numerical instability of transfer matrix method. By operating with total stresses and displacements, it also preserves the convenience for incorporating imperfect or perfect interfaces. However, unlike the stiffness matrix, the hybrid matrix remains to be well-conditioned and accurate even for zero or small thicknesses. The stability of hybrid matrix method has been demonstrated by the numerical results of reflection and transmission coefficients. These results have been determined efficiently based on the surface hybrid matrix method involving only a subset of hybrid submatrices. In conjunction with the recursive asymptotic method, the hybrid matrix method is self-sufficient without hybrid asymptotic method and may achieve low error level over a wide range of sublayer thickness or the number of recursive operations.

Journal Article↗
PubMed2003

Matrix and bioabsorbable polymeric coils accelerate healing of intracranial aneurysms: long-term experimental study.

BACKGROUND AND PURPOSE: Acceleration of intra-aneurysmal clot organization and fibrosis may be a solution to preventing aneurysm recanalization after endovascular treatment. The purpose of this study was to evaluate the short-term efficacy and long-term safety of the new Matrix coil system. METHODS: Matrix coils consist of thin platinum coils covered with a bioabsorbable, polymeric material (polyglycolic acid/lactide). Fifty-two experimental aneurysms were created in 26 swine. All of the aneurysms were tightly packed with Matrix or Guglielmi detachable coils (GDC). Comparative angiographic and histopathologic data were analyzed at 2 weeks (n=14), 3 months (n=6), and 6 months (n=6) after embolization. RESULTS: Three aneurysms treated with GDC ruptured despite tight packing. No recanalization or rupturing was observed in the aneurysms embolized with Matrix coils. At 14 days after embolization, the aneurysms treated with Matrix coils exhibited a more extensive area of organized thrombus when compared with the aneurysms treated with GDC (87% versus 75%, P=0.008, n=11). At 3 months, both Matrix and GDC-treated aneurysms demonstrated complete clot organization. Neck tissue thickness was higher in Matrix-treated aneurysms at 14 days and 3 months, but not at 6 months. No untoward parent artery stenosis was observed in aneurysms treated with Matrix during follow-up. The angiographic cross-sectional area of the Matrix-treated aneurysms was smaller than those treated with GDC at the 3 months. CONCLUSIONS: Matrix accelerated aneurysm fibrosis and neointima formation without parent artery stenosis. The Matrix system might prevent aneurysmal recanalization after endovascular treatment of cerebral aneurysms.

Absorbable Implants↗
PubMed2006

Critical points of DNA quantification by real-time PCR--effects of DNA extraction method and sample matrix on quantification of genetically modified organisms.

BACKGROUND: Real-time PCR is the technique of choice for nucleic acid quantification. In the field of detection of genetically modified organisms (GMOs) quantification of biotech products may be required to fulfil legislative requirements. However, successful quantification depends crucially on the quality of the sample DNA analyzed. Methods for GMO detection are generally validated on certified reference materials that are in the form of powdered grain material, while detection in routine laboratories must be performed on a wide variety of sample matrixes. Due to food processing, the DNA in sample matrixes can be present in low amounts and also degraded. In addition, molecules of plant origin or from other sources that affect PCR amplification of samples will influence the reliability of the quantification. Further, the wide variety of sample matrixes presents a challenge for detection laboratories. The extraction method must ensure high yield and quality of the DNA obtained and must be carefully selected, since even components of DNA extraction solutions can influence PCR reactions. GMO quantification is based on a standard curve, therefore similarity of PCR efficiency for the sample and standard reference material is a prerequisite for exact quantification. Little information on the performance of real-time PCR on samples of different matrixes is available. RESULTS: Five commonly used DNA extraction techniques were compared and their suitability for quantitative analysis was assessed. The effect of sample matrix on nucleic acid quantification was assessed by comparing 4 maize and 4 soybean matrixes. In addition 205 maize and soybean samples from routine analysis were analyzed for PCR efficiency to assess variability of PCR performance within each sample matrix. Together with the amount of DNA needed for reliable quantification, PCR efficiency is the crucial parameter determining the reliability of quantitative results, therefore it was chosen as the primary criterion by which to evaluate the quality and performance on different matrixes and extraction techniques. The effect of PCR efficiency on the resulting GMO content is demonstrated. CONCLUSION: The crucial influence of extraction technique and sample matrix properties on the results of GMO quantification is demonstrated. Appropriate extraction techniques for each matrix need to be determined to achieve accurate DNA quantification. Nevertheless, as it is shown that in the area of food and feed testing matrix with certain specificities is impossible to define strict quality controls need to be introduced to monitor PCR. The results of our study are also applicable to other fields of quantitative testing by real-time PCR.

DNA, Plant↗
PubMed2002

Release from or through a wax matrix system. IV. Generalized expression of the release process for a reservoir device tablet.

Generalization of the release process through the wax matrix layer was examined by use of a reservoir device tablet. The wax matrix layer of the reservoir device tablet was prepared from a physical mixture of lactose and hydrogenated castor oil to simplify the release properties. Release through the wax matrix layer showed zero-order kinetics in a steady state after a given lag time, and could be divided into two stages. The first stage was the formation process of water channel by dissolving the soluble component in the wax matrix layer. The lag time obtained by applying the square root law equation was well connected with the amount of the matrix layer and mixed weight ratio of components in this layer. The second stage was the zero-order release process of drug in the reservoir through the wax matrix layer, because the effective surface area was fixed. The release rate constants were connected with thickness of the matrix layer and permeability coefficient, and the permeability coefficients were connected with the diffusion coefficient of drug and porosity. Hence the release rate constant could be connected with the amount of matrix layer and the mixed weight ratio of components in the matrix layer. It was therefore suggested that the release process could be generalized using the amount of matrix layer and the mixed weight ratio of components in the matrix layer.

Algorithms↗
PubMed1989

Subendothelial matrix of cultured endothelial cells contains fully processed high molecular weight von Willebrand factor.

Von Willebrand factor (vWf) is an adhesive glycoprotein composed of identical subunits linked by disulfide bonds to form multimers of varying sizes. VWf is found in platelets and plasma, where it functions in the adhesion of platelets to exposed subendothelium. Subendothelial matrix contains vWf, but the multimeric composition of matrix vWf, its binding site in matrix, and the mechanism by which it is delivered to matrix are unknown. Using human umbilical vein endothelial cell (HUVE) cultures, we have partially characterized subendothelial matrix vWf. Matrix from HUVE was solubilized in sodium dodecyl sulfate and electrophoresed on 1.25% agarose gels. The extracted vWf was composed of extremely high molecular weight (HMW) multimers of vWf not normally found in plasma. The vWf content of HUVE supernatant, extract, and matrix was quantitated and characterized by radioimmunoassay, agarose gel electrophoresis, and densitometry. The matrix-bound or -associated vWf represented 4% to 18% of total HUVE vWf. Western blot analysis of matrix vWf after reduction showed a subunit species of 220 kd. Long-term incubation of HUVE with phorbol 12-myristate 13-acetate (PMA), a compound that causes release of HMW vWf from Weibel-Palade bodies in HUVE, resulted in a marked decrease in matrix vWf (0.2% to 1% of the total vWf). The multimeric pattern of the remaining matrix vWf continued to show predominantly HMW multimers.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1988

Fibronectin's amino-terminal matrix assembly site is located within the 29-kDa amino-terminal domain containing five type I repeats.

Fibronectin is organized into disulfide cross-linked, insoluble pericellular matrix fibrils by fibroblasts in vitro. Two sites, the Arg-Gly-Asp-Ser-containing cell attachment domain and a site located in the first 70 kDa of fibronectin, are required for matrix assembly. The first 70 kDa of fibronectin contain two structural motifs termed type I and type II homologies, which are repeated nine and two times, respectively. Previous work has implicated the amino-terminal region and the carboxyl terminus containing three type I repeats in matrix assembly, suggesting that type I repeats possess binding activity essential for fibronectin matrix assembly. To test this hypothesis, we developed a sensitive capture immunoassay to quantify insoluble matrix fibronectin and tested a panel of fibronectin fragments, containing all of the type I repeats found in the intact protein, for their ability to inhibit matrix assembly. Only fragments containing the first five type I repeats inhibited fibronectin matrix assembly, although sequences carboxyl-terminal to this domain enhanced this activity. Additional evidence for the specific recognition of the amino-terminal type I repeats by matrix assembling cells was found when the reversible, detergent-sensitive binding of a 125I-labeled fragment containing the first five type I repeats (29 kDa) to cell monolayers was studied. Only monolayers of cell lines that incorporate fibronectin into a fibrillar matrix specifically bound 125I-labeled 29 kDa. Binding of the radiolabeled amino-terminal fragment to matrix-forming cells was inhibited by unlabeled fragments containing the first five type I repeats but not by unlabeled fragments containing the remaining seven type I repeats. Matrix assembly is therefore not a generalized property of type I repeats. Rather, a critical site is located within the first 29 kDa of fibronectin.

Amino Acid Sequence↗