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Blood coagulation factor XIII contributes to the development of traction retinal detachment.

The blood coagulation factor XIII catalyzes the crosslinking of fibrin monomers at the end of the coagulation cascade. Additional functions are the enzymatic coupling of fibrinectin to itself, fibrin, and collagen. We located the two subunits of factor XIII in 20 surgically obtained periretinal membranes, using double label immunofluorescence microscopy. Both subunits of factor XIII could be detected in all specimens. The positive staining in all specimens examined prompted us to determine the source of factor XIII. The abundant fibroblastic cells did not contain factor XIII. Macrophages, half of which stained for the alpha-subunit of factor XIII could not account for the presence of factor XIII because these cells were not present in all specimens, and did not stain for the beta-subunit. Factor XIII is probably derived from the exudation of plasma and platelets through disrupted blood-ocular barriers. This is confirmed by the detection of both subunits in vitreous aspirates from patients with proliferative intraocular disorders (n = 15) by Western blotting.

Antibodies, Monoclonal↗

Application of HUMF13A01 (AAAG)n STR polymorphism to the genetic diagnosis of coagulation factor XIII deficiency.

Deficiency of the A subunit of coagulation factor XIII causes a severe bleeding disorder requiring life long replacement therapy. The mutations causing A subunit deficiency appear to be very heterogeneous, and it is impractical to identify each mutation before genetic counselling or prenatal diagnosis can be attempted. In this study we have shown that a highly polymorphic short tandem repeat element, HUMF13A01 (AAAG)n that occurs in the 5' flanking sequence of the factor XIII A subunit gene, can be used to follow the segregation of deficiency causing mutations. We studied 6 families with factor XIII A subunit deficiency from 5 different ethnic groups. All parents were heterozygous for the repetitive element and therefore all the families were informative. The linked polymorphism was used to carry out the first prenatal diagnosis of factor XIII A subunit deficiency. The analysis of this polymorphism by the polymerase chain reaction is rapid, reliable, requires little DNA and is ideal for the genetic analysis of factor XIII A subunit deficiency.

Factor XIII↗

[3 operated cases of congenital deficiency of Factor XIII associated with intracranial hematomas].

Three operated cases of congenital deficiency of factor XIII (fibrin-stabilizing factor) associated with intracranial hematomas were described and the diagnosis, replacement therapy of the factor were discussed. Congenital deficiency of factor XIII is quite rare coagulation disorder and only 100 patients were reported in the literatures in which we could find only one case who had craniotomy for associated intracranial hemorrhage. Case 1: A 41-year-old female with the history of unknown hemorrhagic diathesis complained of headache and right hemiparesis on August 2, 1980. CT scan showed left parietal intracerebral hematoma caused by unknown hemorrhagic diathesis and operated on under fresh blood transfusion. Postoperative state was uneventful but bleeding from the operated wound and rebleeding in the operated hematoma cavity were found on 5th postoperative day. The screening test for factor XIII was abnormal but replacement therapy with fresh plasma and factor XIII failed to control hemorrhagic diathesis. The patients died of GI bleeding and recurrent intracerebral hematoma on 21st postoperative day. Case 2: A 1.4-year-old boy with the history of umbilical bleeding on delivery and diagnosed as congenital deficiency of factor XIII in the other hospital fall down and struck his occiput on September 20, 1980. He vomited and became stuporous two days after injury, and was transferred to Ryukyu University Hospital. CT can revealed epidural hematoma at the left posterior fossa which extended to the supratentorium. The hematoma was successfully evacuated under infusion of fresh plasma and he showed uneventful recovery without rebleeding by postoperative appropriate replacement therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Contact activation of blood coagulation is inhibited by plasma factor XIII b-chain.

The effect of the purified bovine plasma factor XIII b-chain on contact activation of blood coagulation was studied in human and bovine plasma using either an ellagic acid-phospholipid suspension (Cephotest) or dextran sulfate as activating surface. Contact activation was monitored by the generation of amidolytic activity towards a synthetic chromogenic substrate (S-2302) for factor XIIa and plasma kallikrein. The factor XIII b-chain, which is released from tetrameric factor XIII (a2b2) in the late stages of blood coagulation, inhibits contact activation induced by both activation surfaces mentioned. It was shown that a 5 min preincubation of the factor XIII b-chain with the activation surface increases its inhibitory effect. Light scattering measurements indicated a concurrent binding of the factor XIII b-chain to the Cephotest material. Because factor XIII (a2b2) itself had no such inhibitory activity, the present finding that the factor XIII b-chain inhibits contact activation may point to a novel feed-back inhibition mechanism of blood coagulation.

Animals↗

Platelet vinculin: a substrate of activated factor XIII.

In addition to plasma, Factor XIII of blood coagulation (FXIII) is also present in the cytosol of platelets, monocytes and macrophages. However, its intracellular function has not yet been revealed. Activated Factor XIII (FXIIIa) is a transglutaminase (protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.13) of highly restricted substrate specificity with only a few known protein substrates. In this report, we showed that FXIIIa can link dansylcadaverine, radiolabelled histamine and putrescine to vinculin. Quantitative determinations revealed that in the vinculin molecule a single glutamine residue can serve as acyl donor for the incorporation of small-molecular-weight amines. Vinculin could not be crosslinked to another vinculin molecule. It could be covalently bound, however, to fibrinogen, which indicates that the acyl donor glutamine residue can be engaged in an epsilon-(gamma-glutamyl)lysyl crosslink formation. Since it has been shown that platelet actin and myosin, two main components of cytoskeleton, are also substrates for FXIIIa, and that vinculin is associated to the cytoskeleton during platelet activation, the involvement of FXIII in the stabilization of cytoskeleton at certain phases of cellular function is a likely possibility.

Animals↗

[Is the use of factor XIII for delayed wound healing in patients with head-neck tumors of value?].

BACKGROUND: Factor XIII is known to play an important role in wound healing. In patients with head and neck carcinomas there is an accumulation of risk factors for factor XIII deficiency such as chronic liver disease, extensive tissue lesions, and high intraoperative blood loss. METHOD: Serum levels of factor XIII in 22 patients who had undergone tumor surgery for head and neck carcinoma were measured preoperatively and daily up to 1 week following surgery. Factor XIII was measured with the Berichrome assay as part of our routine laboratory studies. The results were correlated with preoperative pseudocholinesterase (PChe). Factor XIII was substituted for 3 days in 8 patients with persistent wound healing problems that did not improve after two weeks of conservative treatment. RESULTS: We found that PChe levels are a predictor for the development of factor XIII levels during this period. In patients (n = 14) with normal PChe, factor XIII levels reached 86% of the preoperative values 1 week after operation (group 1). In patients (n = 8) with low PChe, the levels reached only 65% (group 2). The rate of wound healing problems was higher in group 2 (6/8) than in group 1 (2/14). In 6 patients treated with factor XIII, the wounds healed within 3 to 7 days. In two cases revision operation was necessary. CONCLUSION: We conclude that the therapy with factor XIII may be successful in patients with wound healing problems. Further studies will be necessary to find out whether prophylactic substitution of factor XIII in patients with low preoperative pseudocholinesterase levels is useful.

Adult↗

Role of factor XIII in fibrin clot formation and effects of genetic polymorphisms.

Factor XIII and fibrinogen are unusual among clotting factors in that neither is a serine protease. Fibrin is the main protein constituent of the blood clot, which is stabilized by factor XIIIa through an amide or isopeptide bond that ligates adjacent fibrin monomers. Many of the structural and functional features of factor XIII and fibrin(ogen) have been elucidated by protein and gene analysis, site-directed mutagenesis, and x-ray crystallography. However, some of the molecular aspects involved in the complex processes of insoluble fibrin formation in vivo and in vitro remain unresolved. The findings of a relationship between fibrinogen, factor XIII, and cardiovascular or other thrombotic disorders have focused much attention on these 2 proteins. Of particular interest are associations between common variations in the genes of factor XIII and altered risk profiles for thrombosis. Although there is much debate regarding these observations, the implications for our understanding of clot formation and therapeutic intervention may be of major importance. In this review, we have summarized recent findings on the structure and function of factor XIII. This is followed by a review of the effects of genetic polymorphisms on protein structure/function and their relationship to disease.

Blood Coagulation↗

Association of a common polymorphism in the factor XIII gene with myocardial infarction.

Factor XIII when activated by thrombin, crosslinks fibrin, however its role in thrombotic disorders is unknown. A common point mutation (G-->T) in exon 2 of the A-subunit gene which codes for an amino acid change three amino acids from the thrombin activation site (Factor XIIIVal34Leu) is a candidate for a role in the pathogenesis of acute myocardial infarction. Factor XIII genotype frequencies were determined in a case-control study of 398 caucasian patients and 196 healthy controls. Patients had undergone angiography for investigation of coronary artery disease and were evaluated for a history of myocardial infarction. The prevalence of the mutation was lower in patients with myocardial infarction than without (32% vs. 50%), p = 0.0009 and than in controls (32% vs. 48%), p = 0.005. Patients possessing the mutation with a history of myocardial infarction had higher PAI-1 concentrations (mean, 27.9 vs. 16.7 ng/ml, p = 0.004) and the PAI-1 4G/4G genotype was commoner (43% vs. 26%, p = 0.03). There was no difference in PAI-1 4G/4G genotype (33% vs. 32%) and PAI-1 levels (mean, 21.0 vs. 20.9 ng/ml) in patients possessing wild type with MI compared to those without MI. These results indicate that the G-->T mutation coding for factor XIIIVal34Leu is protective against myocardial infarction and suggest a mechanism whereby elevated levels of PAI-1 may contribute to vascular risk.

Case-Control Studies↗

b-chains prevent the proteolytic inactivation of the a-chains of plasma factor XIII.

While the transglutaminase activity is associated exclusively with the thrombin-cleaved a chains of plasma Factor XIII, there is little information regarding the role of the b-chains. The present investigations were undertaken to clarify the role of the b-chains during proteolytic activation of plasma factor XIII a-chains. The a-chains of platelet Factor XIII (a2) were extremely sensitive to alpha-thrombin proteolysis, especially in the presence of 5 mM EDTA, resulting in two major fragments with molecular masses 51 +/- 3 kDa and 19 +/- 4 kDa. Furthermore, fibrin enhanced the alpha-thrombin proteolysis of thrombin-cleaved platelet Factor XIII a-chains in presence of CaCl2 or EDTA, resulting in several peptide fragments with molecular masses from 51 +/- 3 kDa to 14 +/- 4 kDa. By contrast, thrombin-cleaved a-chains of plasma Factor XIII (a2b2) were not further degraded by alpha-thrombin in presence of 5 mM EDTA. Even in the combined presence of 5 mM EDTA and 0.1 mg/ml fibrin, alpha-thrombin proteolysis of plasma Factor XIIIa was limited to the formation of a 76 kDa fragment (= Factor XIIIa), a 51 +/- 3 kDa fragment and trace amounts of a 14 +/- 4 kDa species. Platelet Factor XIII proteolyzed by 500 nM alpha-thrombin in presence of 5 mM EDTA expressed less than 20% of enzymatic activity obtained when platelet Factor XIII was activated in presence of 5 mM CaCl2. In contrast, plasma Factor XIII activated by 500 nM apha-thrombin in presence of 5 mM EDTA expressed nearly 65% of original transglutaminase activity. Likewise, when plasma Factor XIII was proteolyzed by 100-1000 nM gamma-thrombin in presence of 5 mM CaCl2 or 5 mM EDTA, maximal transglutaminase activity was observed. However, when platelet Factor XIII was similarly treated with gamma-thrombin in presence of 5 mM EDTA, only one-half the original transglutaminase activity was obtained. The b-chains thus appear to mimic the function of Ca2+ in preserving transglutaminase activity of thrombin-cleaved a-chains. The b-chains of plasma Factor XIII were not degraded by either alpha- or gamma-thrombin treatment, in presence of 5 mM EDTA or 5 mM CaCl2. Both platelet and plasma Factor XIII a-chains were degraded by trypsin to fragments with molecular masses of 51 +/- 3 kDa and 19 +/- 4 kDa in presence of 5 mM CaCl2 and to fragments with molecular masses of 19 +/- 4 kDa and lower, in presence of 5 mM EDTA.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Platelets↗

Roles of low specificity and cofactor interaction sites on thrombin during factor XIII activation. Competition for cofactor sites on thrombin determines its fate.

Factor XIII is activated by thrombin, and this reaction is enhanced by the presence of fibrin(ogen). Using a substrate-based screening assay for factor XIII activity complemented by kinetic analysis of activation peptide cleavage, we show by using thrombin mutants of surface-exposed residues that Arg-178, Arg-180, Asp-183, Glu-229, Arg-233, and Trp-50 of thrombin are necessary for direct activation of factor XIII. These residues define a low specificity site known to be important also for both protein C activation and for inhibition of thrombin by antithrombin. The enhancing effect of fibrinogen occurs as a consequence of its conversion to fibrin and subsequent polymerization. Surface residues of thrombin further involved in high specificity fibrin-enhanced factor XIII activation were identified as His-66, Tyr-71, and Asn-74. These residues represent a distinct interaction site on thrombin (within exosite I) also employed by thrombomodulin in its cofactor-enhanced activation of protein C. In competition experiments, thrombomodulin inhibited fibrin-enhanced factor XIII activation. Based upon these and prior published results, we propose that the polymerization process forms a fibrin cofactor that acts to approximate thrombin and factor XIII bound to separate and complementary domains of fibrinogen. This enables enhanced factor XIII activation to be localized around the fibrin clot. We also conclude that proximity to and competition for cofactor interaction sites primarily directs the fate of thrombin.

Binding, Competitive↗

Plasma transglutaminase factor XIII induces microvessel ingrowth into biodegradable hydroxyapatite implants in rats.

Coagulation factor XIII is a member of the transglutaminase-family. Transgluaminases cross-link either fibrin monomers in blood coagulation or extracellular proteins in extracellular matrix formation. In early stages of bone healing migration and proliferation of endothelial cells lead to formation of new vessels. The aim of this study was to investigate the angiogenetic activity of plasma factor XIII in bone defects filled with nanoparticulate hydroxyapatite paste. A critical size defect was created in the tibial head of rats which was not filled in group I. In group II the defect was filled with hydroxyapatite paste, and in group III with hydroxyapatite paste enriched with factor XIII. Ten days after surgery angiogenesis in the defects was assessed using immunohistochemistry and confocal laser scanning microscopy. Ac16 antibody was used to detect activation of factor XIII into factor XIIIA. In defects without biomaterial (group I) vessel-rich connective tissue and diffuse distribution of capillaries was observed. In defects filled with pure hydroxyapatite (group II) formation of capillaries was limited to the host bone-hydroxyapatite interface. In contrast, addition of plasma factor XIII to hydroxyapatite (group III) stimulated formation of vessels within the biomaterial. The current study reveals that factor XIII can improve angiogenesis in hydroxyapatite.

Absorbable Implants↗

[Changes of factor XIII a and b subunit in patients with disseminated intravascular coagulation syndrome].

Factor XIII is composed of two distinct proteins, a and b subunit. The dimers of each subunit form a tetrameric complex of a2b2 in plasma. Two separate ELISA systems were developed to measure either factor XIII a or b subunit in plasma. Sensitivity of the ELISAs was 3.0% of factor XIII a and b subunit in normal plasma. The ELISA for factor XIII b subunit quantitate free b2 and a2b2 complex in a equimolar manner. In order to evaluate the changes of each factor XIII subunit in a state of hypercoagulation, 16 plasmas from proteins with disseminated intravascular coagulation syndrome (DIC) were examined. Factor XIII a and b subunit showed 56.5 +/- 30.5% and 63.4 +/- 22.5%, respectively in the DIC subjects compared to normal pooled plasma as 100%. The ratio of factor XIII a and b subunit (a/b ratio) were between 0.5 and 1.0 in DIC cases which improved after treatment. However, the ratios were less than 0.5 in the cases with DIC which deteriorated in spite of the treatment. These results suggest that the a/b ratio would indicate the prognosis of patients with DIC.

Biomarkers↗

Factor XIII expression in the skin: observations and a hypothesis.

Factor XIII, a transglutaminase whose best-known function is in the coagulation cascade, is widely distributed in tissues. Three patterns of expression are found in the skin: (1) in cells in an angiocentric pattern around superficial vessels, (2) in early reparative lesions that result in fibroplasia, and (3) in certain sessile neoplasms. Around superficial vessels factor XIII probably stabilizes fibrin clots and helps to seal superficial wounds. On the basis of patterns of expression in evolving reparative lesions, factor XIII likely has an important but still undefined function in the development of fibroplasia. Factor XIII's proposed role in the promulgation of fibroplasia would be integral to the production of the stromal component of small neoplasms that is known to be associated with factor XIII expression.

Biopsy↗

Factor XIII modulates intestinal epithelial wound healing in vitro.

BACKGROUND: An acquired deficiency of blood coagulation factor XIII has been proposed to cause an impairment of intestinal wound healing and hemostasis in patients with inflammatory bowel diseases. Substitution of factor XIII seems to result in a rapid improvement of intestinal wound healing. Our aim was therefore to characterize the role of factor XIII in the modulation of intestinal wound healing in vitro. METHODS: Factor XIII was added to subconfluent cultures of two non-transformed small-intestinal epithelial cell lines (IEC-6, IEC-18) and three human colon cancer-derived epithelial cell lines (T84, CaCo-2, HT-29) with subsequent assessment of cell proliferation with a colorimetric 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenylformazan (MTT) assay. The effects on epithelial cell migration in vitro were assessed with an in vitro wounding model of confluent IEC-6 cell monolayers. RESULTS: Factor XIII caused a modest inhibition of proliferation of IEC-6 and IEC-18 cells. However, factor XIII significantly stimulated proliferation of T84, CaCo-2. and HT-29 cell lines. In addition, thrombin-activated factor Xill promoted intestinal epithelial cell restitution in vitro on average 2.5-fold. The modulatory effects of factor XIII could not be significantly blocked by anti-transforming growth factor beta (TGFbeta). CONCLUSIONS: Factor XIII may promote intestinal epithelial wound healing by enhancement of epithelial cell restitution through a TGFbeta-independent pathway. This may explain previously described beneficial effects of factor XIII in the treatment of active ulcerative colitis.

Animals↗

On the activation of bovine plasma factor XIII. Amino acid sequence of the peptide released by thrombin and the terminal residues of the subunit polypeptides.

A blood coagulation factor, Factor XIII, was highly purified from bovine fresh plasma by a method similar to those used for human plasma Factor XIII. The isolated Factor XIII consisted of two subunit polypeptides, a and b chains, with molecular weights of 79,000 +/- 2,000 and 75,000 +/- 2,000, respectively. In the conversion of Factor XIII to the active enzyme, Factor XIIIa, by bovine thrombin [EC 3.4.21.5], a peptide was liberated. This peptide, designated tentatively as "activation peptide," was isolated by gel-filtration on a Sephadex G-75 column. It contained a total of 37 amino acid residues with a masked N-terminal residue and C-terminal arginine. The whole amino acid sequence of "Activation peptide" was established by the dansyl-Edman method and standard enzymatic techniques, and the masked N-terminal residue was identified as N-acetylserine by using a rat liver acylamino acid-releasing enzyme. This enzyme specifically cleaved the N-acetylserylglutamyl peptide bond serine and the remaining peptide, which was now reactive to 1-dimethylamino-naphthalene-5-sulfonyl chloride. A comparison of the sequences of human and bovine "Activation peptide" revealed five amino acids replacements, Ser-3 to Thr; Gly-5 to Arg; Ile-14 to Val; Thr-18 to Asn, and Pro-26 to Leu. Another difference was the deletion of Leu-34 in the human peptide. Adsorption chromatography on a hydroxylapatite column in the presence of 0.1% sodium dodecyl sulfate was developed as a preparative procedure for the resolution of the two subunit polypeptides, a or a' chain and b chain, constituting the protein molecule of Factor XIII or Factor XIIIa. End group analyses on the isolated pure chains revealed that the structural change of Factor XIII during activation with thrombin occurs only in the N-terminal portion of the a chain, not in the N-terminal end of the b chain or in the C-terminal ends of the a and b chains. From these results, it was concluded that the activation of bovine plasma Factor XIII by thrombin must be accompanied by a limited proteolysis of the arginyl-glycyl bond located in the N-terminal region of the a chain, liberating the "Activation peptide." The possibility of activating Factor XII with other porteinases was examined using Factor Xa [EC 3.4.21.6], Factor XIIa, kallikreins [EC 3.4.21.8], urokinase [EC 3.4.99.26], trypsin [EC 3.4.21.4], ficin [EC 3.4.22.3], papain [EC 3.4.22.2], and bromelain [EC 3.4.22.4]. Among these enzymes, only bromelain and trypsin showed clear activating effects.

Amino Acid Sequence↗

Role of calcium ion in the generation of factor XIII activity.

The involvement of calcium ion in the activation of both plasma factor XIII (alpha 2 beta 2) and platelet factor XIII (alpha 2) was investigated. The second-order dependence of the rate constant for exposure of the active-site thiol group of alpha-thrombin-cleaved plasma factor XIII (alpha 2'beta 2) on the concentration of calcium ion suggested that the binding of two calcium ions is required for transformation of the alpha 2'beta 2 tetramer to enzymatically active factor XIIIa. Fibrinogen, previously reported to lower the calcium ion concentration required for efficient activation of alpha 2'beta 2 [Credo, R. B., Curtis, C. G., & Lorand, L. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4234-4237], was found in the present study to increase the rate of exposure of the active-site thiol group. Whereas calcium ion is required for exposure of the active-site thiol group in cleaved plasma factor XIII (alpha 2'beta 2), exposure of an active-site thiol group in cleaved platelet factor XIII (alpha 2') occurs in the absence of calcium ion. The rate constant (2.2 x 10(5) M-1 s-1) for alpha-thrombin-catalyed exposure of the active-site thiol group of platelet factor XIII zymogen (alpha 2) in the presence of calcium ion was greater than the rate constant (0.7 x 10(5) M-1 s-1) determined in the absence of calcium ion.(ABSTRACT TRUNCATED AT 250 WORDS)

Allosteric Regulation↗

Coagulation factor XIII and markers of thrombin generation and fibrinolysis in patients with inflammatory bowel disease.

OBJECTIVE: To relate factor XIII levels and other prothrombotic markers to inflammatory bowel disease and investigate the frequency of valine34leucine and its effect on factor XIII cross-linking activity in patients with inflammatory bowel disease. DESIGN: Fifty patients with active inflammatory bowel disease but no venous thromboembolism (32 with ulcerative colitis, 18 with Crohn's disease), 50 patients with inactive inflammatory bowel disease but no venous thromboembolism (32 with ulcerative colitis, 18 with Crohn's disease), two age- and gender-matched healthy control groups of 100 subjects each were recruited. To further explore the relationship between valine34leucine and inflammatory bowel disease, 21 patients with the disease (13 with ulcerative colitis and eight with Crohn's disease) and venous thromoembolism (male to female ratio = 7 : 14, median age 59.5 years (range, 19-80 years)) were recruited. Two hundred and fifteen control subjects (M : F = 121 : 94, median age 62 years (28-74 years)), with venous thromboembolism (119 with deep venous thrombosis, and 96 with pulmonary embolism) were drawn from the same geographical area as the patients. METHODS: Factor XIII A, B-subunit antigen and A2B2 tetramer levels were measured using an in-house sandwich enzyme-linked immunoassay method. RESULTS: Factor XIII A2B2 tetramer and the A-subunit were significantly decreased in patients with active inflammatory bowel disease compared with controls (59% vs 95%, P < 0.0001 and 75% vs 102%, P < 0.0001, respectively), but not between the inactive inflammatory bowel disease group and controls. The D-dimer and prothrombin 1+2 fragment levels in patients with active inflammatory bowel disease were raised compared with controls (178 (152) vs 109 (84), P = 0.0007 and 82 (43) vs 55 (28), P = 0.0001, respectively). The factor XIII B-subunit and factor XIII cross-linking activity were not significantly different between patients with active or inactive inflammatory bowel disease and controls. There was no significant difference in genotype distribution in inflammatory bowel disease patients with or without venous thromboembolism and respective control subjects. Levels of tissue plasminogen activator antigen were significantly increased in patients with active inflammatory bowel disease when compared to inactive inflammatory bowel disease and controls (8.9 (3.7) vs 6.7 (3.4) vs 6.9 (3.4), P < 0.001). CONCLUSIONS: Active inflammatory bowel disease is associated with activation of coagulation. Factor XIII A and A2B2 tetramer levels were markedly decreased in active inflammatory bowel disease. Variations in the level of factor XIII in patients with inflammatory bowel disease could be multifactorial and in part may result from the increased formation of microthrombi and accelerated turnover of the factor XIII. We found no evidence of association of factor XIII valine34leucine polymorphism and inflammatory bowel disease.

Case-Control Studies↗

Colorimetric assay of blood coagulation factor XIII in plasma.

In this new colorimetric assay for Factor XIII in plasma, 5-(biotinamido)pentylamine is used as the amine substrate. Factor XIII, a zymogen, is transformed by thrombin and Ca2+ to active Factor XIIIa, and the incorporation of 5-(biotinamido)pentylamine into N,N-dimethylcasein is used to measure catalytically active Factor XIIIa. The biotinylated enzymatic product is immobilized onto 96-well microtiter plates, complexed with streptavidin-beta-galactosidase, and the absorbance at 405 nm is monitored for production of p-nitrophenol from p-nitrophenyl-beta-D-galactopyranoside. Concentrations of N,N-dimethylcasein, 5-(biotinamido)pentylamine, Ca2+, and thrombin were chosen to allow near-maximum velocity of amine incorporation. A linear relationship was obtained between assay product and plasma volume, from 0.5 to 50 microL of plasma. Results correlated well (r greater than 0.924) with those from the most frequently utilized radiometric filter-paper assay for Factor XIII. The method appears to be ideal for routine diagnostic estimation of Factor XIII in plasma because of its simplicity, its lack of use of radioisotopes, and its potential for assay of large numbers of samples by use of microtiter plates and automated plate readers.

Calcium↗