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PubMed1999

Angiotensin II-induced transactivation of epidermal growth factor receptor regulates fibronectin and transforming growth factor-beta synthesis via transcriptional and posttranscriptional mechanisms.

The signaling cascade elicited by angiotensin II (Ang II) resembles that characteristic of a growth factor, and recent evidence indicates transactivation of epidermal growth factor receptor (EGF-R) by G protein-coupled receptors. Here, we report the involvement of EGF-R in Ang II-induced synthesis of fibronectin and transforming growth factor-beta (TGF-beta) in cardiac fibroblasts. Ang II stimulated fibronectin mRNA levels dose dependently, with a maximal increase (approximately 5-fold) observed after 12 hours of incubation. Fibronectin synthesis induced by Ang II or calcium ionophore was completely abolished by tyrosine kinase inhibitors and intracellular Ca2+ chelating agents. Ang II-induced fibronectin mRNA was not affected by protein kinase C inhibitors or protein kinase C depletion, whereas specific inhibition of EGF-R function by a dominant negative EGF-R mutant and tyrphostin AG1478 abolished induction of fibronectin mRNA. We isolated the rat fibronectin gene, including the 5'-flanking region, and found that the activator protein-1 (AP-1) binding site present in the promoter region was responsible for the Ang II responsiveness of this gene. A gel retardation assay revealed the binding of nuclear protein to the AP-1 site, which was supershifted with anti-c-fos and anti-c-jun but not anti-activating transcription factor (ATF)-2 antibodies. Conditioned medium from Ang II-treated cells contained TGF-beta bioactivity, and addition of neutralizing TGF-beta antibody modestly (46%) inhibited induction of fibronectin. Ang II-induced synthesis of TGF-beta was also abolished by inhibition of EGF-R function. The effect of TGF-beta was exerted by stabilizing fibronectin mRNA without affecting the promoter activity and required de novo protein synthesis. We concluded that Ang II-induced expression of fibronectin and TGF-beta is mediated by downstream signaling of EGF-R transactivated by Ca2+-dependent tyrosine kinase and that Ang II-induced fibronectin mRNA expression is regulated by 2 different mechanisms, which are transcriptional control by binding of the c-fos/c-jun complex to the AP-1 site and posttranscriptional control by mRNA stabilization due to autocrine or paracrine effects of TGF-beta. Thus, this study suggests that the action of Ang II on extracellular matrix formation should be interpreted in association with the EGF-R signaling cascade.

Angiotensin II↗
PubMed1996

Fibronectin matrix formation by human fibroblasts on surfaces varying in wettability.

The spatial organization of extracellular fibronectin on biomaterial surfaces might be important for interaction with tissue cells. In previous investigations we have demonstrated that hydrophilic materials bind preadsorbed fibronectin that can easily be reorganized by fibroblasts in a specific matrix-like structure, while on less wettable materials (possessing water contact angles above 60 deg) the cells were unable to do this. As the cells continuously produce their fibronectin matrix, we tried in this study to answer the question of how the surface wettability of biomaterials influences the endogenous fibronectin matrix formation and its subsequent organization on the substrate. We cultured fibroblasts for 72 h on five different wettable surfaces: glass, aminopropyltriethoxysilane, pellethane, polyvinylchloride, and silicone, with water-contact angles gradually ranging from 25 to 105 deg. We demonstrated that the decreasing wettability of the materials significantly reduced endogenous fibronectin deposition on the substratum. Moreover, fibrillar organization of fibronectin appeared only on relatively hydrophilic glass and APS substrate, while on more hydrophobic materials like PVC and SI, cells secreted some fibronectin but were not able to organize it into a fibronectin matrix. These results were correlated with an altered cell morphology and spreading on these materials. In addition, an ELISA method has been implemented to quantify fibronectin matrix formation as a possible measure of the biocompatibility of materials, where a clear relation has been found between fibroblast growth and fibronectin matrix formation.

Adsorption↗
PubMed1988

Fibronectin degradation products containing the cytoadhesive tetrapeptide stimulate human neutrophil degranulation.

We investigated whether adhesive glycoproteins, such as fibronectin or fibrinogen, could function to provide a nidus for neutrophil degranulation. Elastase release in recalcified plasma was normal in afibrinogenemic plasma, but 73% less in plasma depleted of fibronectin. Proteolytic digests of fibronectin, but not intact fibronectin (50-1,000 micrograms/ml), induced a concentration-dependent release of neutrophil elastase and lactoferrin. MAbs N293, which recognized the mid-molecule of fibronectin, N294, which was directed toward the 11-kD cell adhesive fragment, and N295, generated against the amino terminal of the 11-kD fragment, inhibited the release of elastase by 7, 24, and 60%, respectively. The cytoadhesive tetrapeptide portion of fibronectin, Arg-Gly-Asp-Ser (250-1,000 micrograms/ml), released 1.94 +/- 0.10 micrograms/ml of elastase from 10(7) neutrophils, in contrast to the lack of release by the control hexapeptide, Arg-Gly-Tyr-Ser-Leu-Gly. Plasmin appeared to be the enzyme responsible for fibronectin cleavage, since neutrophil elastase release in plasma that had been depleted of plasminogen was decreased and reconstitution of plasminogen-deficient plasma with purified plasminogen corrected the abnormal release. Plasmin cleaved fibronectin to multiple degradation products, each less than 200 kD. This fibronectin digest released 1.05 microgram/ml of elastase from 10(7) neutrophils. We suggest that the activation of plasminogen leads to the formation of fibronectin degradation products capable of functioning as agonists for neutrophils.

Antibodies, Monoclonal↗
PubMed1989

Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation.

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.

Adult↗
PubMed1983

Normal fibronectin levels as a function of age in the pediatric population.

Fibronectin is an important non-immune opsonic protein influencing phagocytic clearance of blood-borne nonbacterial particulates which may arise in association with septic shock, tissue injury, and intravascular coagulation. In the present study, serum fibronectin was measured by both electroimmunoassay as well as rapid immunoturbidimetric assay in healthy children (n = 114) ranging in age from 1 month to 15 years in order to delineate the temporal alterations in fibronectin with age. Normal adult serum fibronectin concentrations are typically 220 micrograms/ml +/- 20 micrograms/ml. Serum concentration is 35-40% lower than normal plasma concentration due to the binding of fibronectin to fibrin during clot formation. Children between 1-12 months of age had significantly (P less than 0.05) lower serum fibronectin levels than children between the ages of 1-15 years. Progressive elevation in fibronectin levels was observed within the last 8 months of the first year of age. Fibronectin levels in children older than 1 year of age remained constant up to 15 years and were within the lower limit of the normal adult concentration. No significant (P greater than 0.05) difference in serum fibronectin was observed between male and female children at all age groups. Fibronectin levels thus, increase during the first year of age and normal levels of this blood protein in the infant are less than the normal range for adults.

Adolescent↗
PubMed1985

Fibronectin as a marker of granulosa cell cytodifferentiation.

The hormonal regulation of fibronectin secretion by rat granulosa cells in culture was investigated: fibronectin was measured by a competitive enzyme-linked immunoadsorbant assay. Granulosa cells isolated from 25-day-old diethylstilbestrol-primed rats and cultured under defined conditions in the absence of hormones secreted low levels of fibronectin during the first 24 h of culture, after which there was a rapid increase in secretion until 72 h. In contrast, cultures treated with a combination of NIH-FSH-15 (200 ng/ml) and insulin (5 micrograms/ml) secreted low levels of fibronectin throughout the culture period. Subsequently, it was found that both FSH and insulin could independently suppress the increase in fibronectin secretion found in control cultures. Combined treatment with FSH and insulin resulted in a level of fibronectin which was the same as either FSH or insulin alone. The actions of FSH and insulin were dose dependent; 10 ng FSH/ml and 2.5 micrograms insulin/ml were required to produce a maximum suppression. The ability of (Bu)2cAMP (1.0 mM) to suppress fibronectin secretion suggested that the action of FSH on this parameter was mediated via the production of cAMP. Testosterone and estrogen alone did not influence secretion and did not modulate the actions of FSH and insulin. At the time at which FSH induces the cytodifferentiation of granulosa cells in culture, assessed by the increase in aromatase activity, fibronectin secretion is suppressed. The inverse relationship between fibronectin secretion and the induction of those granulosa cell functions essential for the development of the preovulatory follicle indicates that fibronectin may provide a useful marker for the stage of cytodifferentiation and follicular maturation.

Animals↗
PubMed1991

Arrangement of cellular fibronectin in noncollagenous fibrils in human fibroblast cultures.

The assembly of fibronectin into fibrils was examined by high-voltage immunoelectron microscopy in subconfluent cultures of ascorbate-treated human skin fibroblasts. Cells grown in the presence of ascorbic acid for 24, 48 or 72 h were labeled with Ist-9, a monoclonal antibody specific for the EIIIA site in fibronectin, and polyclonal antibodies to type I collagen. Cells were then labeled with goat anti-mouse IgG and goat anti-rabbit IgG coupled to 5 or 18 nm colloidal gold beads. Our results show that by 24 h, fibronectin is observed in fibrils in the extracellular matrix. The majority of fibronectin in fibrils does not co-localize with type I collagen. Morphometric analysis of the distance between EIIIA sites in fibronectin fibrils (less than 12 nm in diameter) show that the EIIIA sites appear to be spaced approximately 84 nm apart. The distance of 84 nm suggests that fibronectin is fully extended in fibrils and that the amino termini of adjacent fibronectin dimers overlap by 20 nm. As fibronectin fibrils become thicker, the average distance between EIIIA sites in fibronectin dimers decreases to 42 nm. This decrease in the distance between EIIIA sites may be due to a staggering of fibronectin dimers within the fibril as the fibril matures.

Cells, Cultured↗
PubMed1984

Role of glycosaminoglycans and collagen in the development of a fibronectin-rich extracellular matrix in cultured embryonic corneal epithelial cells.

Corneal epithelial cells from 15-day chick embryos produce a fibronectin-rich extracellular matrix when cultured on glass, plastic and fibronectin-coated substrata. Cell culture in the presence of Streptomyces hyaluronidase or chondroitinase ABC resulted in considerable reduction of the matrix; collagenase had a lesser effect but nevertheless also reduced the matrix. In all enzyme treatments the cells attached and spread to form characteristic epithelial cell islands, but the marginal cells of these islands showed a marked reduction in the number of lamellipodia and focal contacts. Also, the immunofluorescent staining pattern for fibronectin was considerably reduced. Control cells cultured on a fibronectin-coated surface were able to reorganize the fibronectin into fibrils, whereas cells cultured in enzymes showed little or no ability to do so. The cellular reorganization of fibronectin could also be inhibited by the addition of L-azetidine-2-carboxylic acid (LACA), an inhibitor of collagen secretion. Cells plated out in the presence of LACA spread much better on collagen substrata than on plastic, glass or fibronectin. However, in all cases very little fibronectin matrix was detectable in the epithelial islands. The results suggest that components of the extracellular matrix (ECM) such as collagen, hyaluronic acid and chondroitin sulphates are not essential for the initial attachment and spreading of corneal epithelial cells in culture, but are important in the development of the ECM, and in maintaining a flattened morphology and spreading behaviour. It is suggested that fibronectin plays an important role in these interactions and that the ability of cells to organize fibronectin into fibrils is dependent on the presence of other ECM components such as glycosaminoglycans and collagen.

Animals↗
PubMed1992

Sequential appearance of fibronectin, collagen and elastin during fatty streak initiation and maturation in hypercholesterolemic fat-fed rabbits.

To elucidate whether tissue fibronectin increases in the early stages of atherogenesis induced by hypercholesterolemia without mechanical trauma, we investigated sequential changes in the distribution of tissue fibronectin during fatty streak initiation and maturation in the aortas of hypercholesterolemic fat-fed rabbits. The presence of fibronectin was examined on immunoperoxidase stained tissue specimens with the aid of a microscope-photometric technique. Twenty male albino rabbits were used. Cholesterol supplemented chow (1%) was given for 4 weeks (n = 6), 8 (n = 5) or 14 weeks (n = 5). A membrane-like layer positive for fibronectin was observed along the endothelium in the normal aorta. After 4 weeks of the cholesterol-feeding, fatty streaks were initiated in the intima, where fibronectin was more densely accumulated than the normal intima. After 8 weeks of the cholesterol-feeding, fatty streaks were expanding, associated with the dense staining for fibronectin. After 14 weeks, fibronectin was still concentrated in the endothelial layer and also in the superficial areas of the thickened intima, but decreased in the deep areas of the thickened intima where collagen and elastin appeared as bundles. The photometric data of fibronectin supported these visual observations. Thus, fibronectin appeared early and disappeared later in the intima during the process of fatty streak initiation and maturation. These findings suggest that in hypercholesterolemia without mechanical endothelial injury, fibronectin may play an important role in an early process of atherogenesis.

Animals↗
PubMed1986

Fibronectin is synthesized as an acute phase reactant in rat hepatocytes.

Elevated concentrations of fibronectin were found in plasma of rats under different acute phase conditions. Untreated animals showed a plasma fibronectin concentration of 150 +/- 50 mg/l, which increased to 412 +/- 59 mg/l 24 h after subcutaneous injection of turpentine. The time course of the changes in plasma fibronectin concentration showed a peak at 24 h and a decline to normal concentrations 72 h after turpentine treatment. Additional stimulation by dexamethasone resulted in plasma fibronectin concentrations of 661 +/- 49 mg/l. No or only slight elevations of fibronectin concentrations were observed after treatment with adrenaline, thyroxine and triiodothyronine as compared with saline-injected animals. The common identity of plasma fibronectin in controls, turpentine and turpentine-dexamethasone-treated animals was shown by slab gel electrophoresis under nonreducing conditions, followed by western blot and immunofluorescence staining. One dimensional immunoelectrophoresis performed with polyclonal antibodies to human fibronectin cross-reacting with rat fibronectin (shown by Ouchterlony gel diffusion) revealed identical precipitation lines for the plasma of control and acute phase animals. Hepatocytes of turpentine-pretreated rats show a threefold increase of [14C]valine incorporation into total protein and a fourfold increase of immunoreactive radioactively labeled fibronectin in the culture medium, compared with control hepatocyte cultures. These results point to the role of hepatocytes in the synthesis of plasma fibronectin, which behaves in rats as an acute phase reactant.

Acute-Phase Proteins↗
PubMed1983

Differences in the carbohydrate moieties of plasma and amniotic fluid fibronectins as revealed by crossed immunoaffinity electrophoresis with concanavalin A.

Human fibronectins isolated from pooled human plasma and amniotic fluid were studied as to differences in their carbohydrate moieties. The chemical analyses showed that amniotic fluid fibronectin is different from adult plasma fibronectin in carbohydrate content and composition while there seems to be no significant differences in amino acid composition. Crossed immunoaffinity electrophoresis with free concanavalin A, as well as rocket immunoelectrophoresis with immobilized concanavalin A intermediate gel, indicated that amniotic fluid fibronectin has little or no reactivity with this lectin while adult plasma fibronectin is strongly reactive. Fetal cord plasma fibronectin apparently interacted with concanavalin A, but its reactivity was weaker than that of adult plasma fibronectin. Fibronectin isolated from ascitic fluid of an ovarian cancer patient which was examined in additional experiments showed much weaker Con A-reactivity than fetal cord plasma fibronectin. These results suggest that fibronectins from various body fluids differ in their carbohydrate structures.

Amino Acids↗
PubMed1999

IgA interaction with carboxy-terminal 43-kD fragment of fibronectin in IgA nephropathy.

IgA deposition in the glomerular mesangial matrix is a prerequisite for the diagnosis of IgA nephropathy, and circulating IgA-containing complex has been implicated in this process. Since fibronectin is known to be involved in the assembly of extracellular matrix, this study was conducted to investigate whether fibronectin and its fragments are present in sera of patients and are capable of binding IgA1. Sera from patients with IgA nephropathy were purified by heparin-affinity chromatography, and column eluate were analyzed for the presence of fibronectin using Western blot and a set of anti-fibronectin monoclonal antibodies. Native fibronectin was digested with cathepsin D to obtain fragments similar to those of serum fibronectin. The capacity of fibronectin to bind IgA was examined with a mixture of purified IgA1 and cathepsin D-digested fibronectin fragments. A 43-kD carboxy-terminal fragment of fibronectin was detected in samples derived from sera of patients with IgA nephropathy but not in healthy control subjects. A similar-sized fragment was generated by cathepsin D digestion of the native molecule and was shown to bind to IgA1 in vitro. Since the carboxy-terminal domain is known to be critical in assembling exogenous fibronectin into the extracellular matrix, the affinity to IgA1 to a fragment found in patients may have pathogenic potential to mediate extracellular IgA deposition in IgA nephropathy.

Chromatography, Affinity↗
PubMed1991

The roles of laminin and fibronectin in the development of the lens capsule.

This study examines the distribution of laminin and fibronectin in the rat lens capsule during development. Both these extracellular matrix glycoproteins are localised in the interspace between presumptive lens and presumptive retina as well as in their basal laminae. The lens capsule arises from multilayering of the basal lamina of the lens cells. Immunofluorescence localises both laminin and fibronectin in the capsule at 16 days of embryonic development, although reactivity for fibronectin is much weaker than for laminin. In the 19 day embryo only laminin is detected. This indicates that during embryonic development fibronectin becomes a minor component of lens cell ECM and is not accumulated in the developing capsule. The roles of laminin and fibronectin in promoting cell migration during development were analysed in explant cultures. Lens epithelial explants from 16, 17 and 19 day old embryos and neonatal rats were grown on a laminin or fibronectin substratum. Lens cells from all ages of rats migrated on the laminin substratum, whereas lens cells progressively lost the ability to migrate on a fibronectin substratum as the age of the donor increased. This developmental loss of ability to migrate on fibronectin in vitro coincides with the developmental loss of fibronectin from the lens capsule in vivo. Therefore, we propose that whilst both laminin and fibronectin may be important for promoting migration of lens cells on their substratum at early stages of lens morphogenesis, during development laminin takes over as the key molecule that promotes migration on the capsule.

Animals↗
PubMed2001

Fibronectin promotes calcium signaling by interferon-gamma in human neutrophils via G-protein and sphingosine kinase-dependent mechanisms.

A common intracellular signal activating polymorphonuclear leukocytes (PMN) in inflammation is a change in cytosolic calcium concentration. Previously, we have shown that interferon-gamma (IFN-gamma) induces transient calcium signals in PMN, but only after intracellular calcium store depletion. Using a digital imaging system, we show that adhesion of PMN is critical for IFN-gamma-induced calcium signals, and with PMN attached to the optimal coating, the calcium signals are evoked even in presence of extracellular calcium, that is, non-depleted calcium stores. Adhesion to fibronectin, pure or extracted from plasma by gelatin, improved the IFN-gamma responses compared with serum, plasma, or vitronectin coats. In accordance with previous observations, IFN-gamma-induced calcium signals in fibronectin adherent cells were totally abolished by the G-protein inhibitor pertussis toxin and were also inhibited by the sphingosine kinase inhibitors dimethylsphingosine (DMS) and N-acetylsphingosine (N-Ac-Sp). PMN contact with fibronectin alone, measured in cells sedimenting onto a fibronectin-coated surface or by addition of fibronectin to glass-adherent cells, evoked transient calcium signals. However, PMN in suspension did not respond to the addition of fibronectin or arginine-glycine-aspartate (RGD). The fibronectin-induced calcium signals were also clearly depressed by pertussis toxin and by the sphingosine kinase inhibitors DMS, dihydrosphingosine (DHS), and N-Ac-Sp. When the product of sphingosine kinase activity, sphingosine 1-phosphate (S1-P), was added to the cells, similar calcium signals were induced, which were dependent on a pertussis toxin-sensitive G-protein activity. Finally, addition of S1-P to the cells prior to stimulation with IFN-gamma partly mimicked the priming effect of fibronectin. In conclusion, fibronectin contact evokes by itself a calcium signal in PMN and further promotes calcium signaling by IFN-gamma. We suggest that fibronectin might activate sphingosine kinase, and that the sphingosine 1-phosphate thereby generated induces a calcium signal via a G-protein-dependent mechanism. Apparently, sphingosine kinase activity is also involved in IFN-gamma induced calcium signals.

Calcium↗
PubMedDate not supplied

[Diagnostic importance of fibronectin in chronic liver diseases].

Plasma fibronectin was determined in 29 patients with decompensated cirrhosis (7 patients had bacterial infection) and 23 patients with malignant liver disease. The obtained values were compared with the fibronectin values in 20 healthy subjects belonging to the control group in order to determine the possible diagnostic value of this dimer glycoprotein of high molecular weight whose role in the organism has not been completely explained. Fibronectin was determined on nephelometer with the use of specific antiserum by Behringwerke. The results expressed as mean values and SD were compared with monofactorial variance analysis (method One-way ANOVA). Fibronectin values in patients with liver cirrhosis were statistically significantly lower than in the control group (p < 0.01), which is also the case with correlation with malignant liver disease (p < 0.01). The fibronectin values in patients with malignant diseases were almost the same as the control group values (p < 0.01). In 7 patients with liver cirrhosis and bacterial infection the fibronectin values were statistically significantly higher in relation to those in the remaining 22 patients with cirrhosis but without bacterial infection (p < 0.001). The investigation in this study indicated that the decrease of mean fibronectin values is related to hepatic failure which is of diagnostic value, while normal values in malignant diseases do not favor the opinion on fibronectin as a tumor marker. Higher fibronectin values in infection in patients with liver cirrhosis are not clear, which indicated the total complexity of the relation between fibronectin as a dimer glycoprotein and chronic liver diseases including malignant.

Bacterial Infections↗
PubMedDate not supplied

[Levels of fetal fibronectin in the cervix and vagina during pregnancy].

INTRODUCTION: Fibronectin is a glycoprotein produced by different types of cells. It can be divided into two main groups--soluble fibronectin, found in human plasma and other body fluids (amniotic fluid) and tissue fibronectin, found in basal membrane and connective tissue between endothelial cells (2). There are three subtypes--plasmatic, cellular and onco-fetal fibronectin, the most important during pregnancy, with different concentrations during the course of pregnancy. The aim of the study is to establish normal distribution of fetal fibronectin in cervicovaginal fluid during pregnancy in our population and afterwards establish the relation between concentrations in different stages of pregnancy and the pregnancy outcome. MATERIAL AND METHODS: This prospective, observational study was done at the Department of Obstetrics and Gynaecology, Clinical Centre Novi Sad, during the period June-October 1988. The presented results are preliminary ones. The patients were randomly chosen from the population that came for routine consultations as well as the ones hospitalized at the Department, at the High Risk Pregnancy Unit, for reasons other than threatening miscarriage and preterm delivery. One-hundred and thirty two pregnant women were examined, divided into three groups, according to gestational age. In group I were women between 7-20 weeks, in group II between 21 and 37 weeks and in group III 38 and more weeks. In every case general and obstetric data were collected, and cervico-vaginal fibronectin was taken from the posterior vaginal fornix, using a special kit (Specimen Collection Package, Adeza Biomedical). Fetal fibronectin concentration was tested using enzyme immunoassay (Adeza Biomedical) and positive was considered the concentration of and above 0.05 microgram/ml. RESULTS: The mean cervico-vaginal fibronectin concentration, uncorrected for the outcome of the pregnancy was as follows--in group I 0.045 (0-0.11) microgram/ml, group II 0.037 (0-1.22) microgram/ml, and in group III 0.226 (0.001-1.05) microgram/ml. The concentration trend was from weakly negative during the period 7-20 weeks, over highly negative (21-37 weeks) to very positive, after 38 weeks. The positive/negative relation in group I was 29.2%/70.8%, group II 11.7%/88.3% and group III 48.4%%/51.6%. After the correction of the results for miscarriages/preterm deliveries/failed induction in postterm pregnancies, the mean concentrations were somewhat different--group I 0.029 microgram/ml, II 0.019 microgram/ml and III 0.282 microgram/ml. The relations of positive and negative results were changed as well and in group I the relation was 27.3%/72.7%, group II 6.8%/93.2% and group III 71.4%/28.6%. DISCUSSION: After the correction for duration and outcome of the pregnancy, our results differed from the results in the literature. Thus in the 1st trimester fetal fibronectin was positive in cervico-vaginal fluid of 27.3% pregnant women, which is double the number usually found in the literature, between 21 and 37 weeks, when a positive result (> 0.05 microgram/ml) would be expected in only 3% of cases, it was positive in 6.8%, whereas 2.3 of the women delivered at term had a positive concentration. The discrepancy in group II (21-37 weeks) cannot be explained neither with a higher incidence of late miscarriages, nor preterm deliveries, for the incidence of such complications was only 3%, which is far less than usually found in the non-selected population (10%) (9). It is also possible that the discrepancy in our results and the results found in literature is based on a fact that our population was not preselected, which was the case in other studies' populations that did not include women with heavy, non-treated vaginal discharge, nor the ones that had sexual intercourse within 24 hours from the moment of fibronectin sampling. (ABSTRACT TRUNCATED)

Adult↗
PubMed2000

[Fibronectin level in amniotic fluid as an index of unavoidable labor].

During uterus contractions detaching of amino-chorionic layer from uterus wall occurs and released fibronectin penetrates into amniotic fluid. The aim of this study was to estimate in a quantity mode the presence of fibronectin in amniotic fluid and to find the dependence between the fibronectin level in amniotic fluid and the period of time from collecting the sample to the labor. We wanted also to find the dependence between fibronectin level in amniotic fluid and duration of pregnancy, preterm rupture of amniotic membranes, patients' age, parity and number of deliveries. We analysed 86 pregnant women where we estimated the fibronectin level in specimens of amniotic fluid. During carrying out the experiment we noted that fibronectin is present in amniotic fluid and can be identified in a quantity mode. We have proved dependence between fibronectin level in amniotic fluid and the period of time from collecting the sample, up to the delivery. Fibronectin level in amniotic fluid in pregnancies uncomplicated with premature delivery was on the average 350 mg/ml. Increase of fibronectin in amniotic fluid above 700 mg/ml points at detaching of amino-chorionic layer and the occurrence of unavoidable preterm labor at the time no longer than 24 hours. Fibronectin level in amniotic fluid doesn't depend of pregnancy duration, preterm rupture of amniotic membranes.

Adult↗
PubMed1991

Fibronectin decreases the stimulatory effect of fibrin and fibrinogen fragment FCB-2 on plasmin formation by tissue plasminogen activator.

Fibronectin is a dimeric glycoprotein (Mr 440,000) involved in many adhesive processes. During blood coagulation it is bound and cross-linked to fibrin. Fibrin binding is achieved by structures (type I repeats) which are homologous to the "finger" domain of tissue plasminogen activator. Tissue plasminogen activator also binds to fibrin via the finger domain and additionally via the "kringle 2" domain. Fibrin binding of tissue plasminogen activator results in stimulation of its activity and plays a crucial role in fibrinolysis. Since fibronectin might interfere with this binding, we studied the effect of fibronectin on plasmin formation by tissue plasminogen activator. In the absence of fibrin, fibronectin had no effect on plasminogen activation. In the presence of stimulating fibrinogen fragment FCB-2, fibronectin increased the duration of the initial lag phase (= time period until maximally stimulated plasmin formation occurs) and decreased the rate of maximal plasmin formation which occurs after that lag phase mainly by increasing the Michaelis constant (Km). These effects of fibronectin were dose-dependent and were similar with single- and two-chain tissue plasminogen activator. They were also observed with plasmin-pretreated FCB-2. An apparent Ki of 43 micrograms/ml was calculated for the inhibitory effect of fibronectin when plasminogen activation by recombinant single-chain tissue plasminogen activator was studied in the presence of 91 micrograms/ml FCB-2. When a recombinant tissue plasminogen activator mutant lacking the finger domain was used in a system containing FCB-2, no effect of fibronectin was seen, indicating that the inhibitory effect of fibronectin might in fact be due to competition of fibronectin and tissue plasminogen activator for binding to fibrin(ogen) via the finger domain.

Fibrin↗