Congenital Deficiency of Plasminogen and Its Relationship to Venous Thrombosis

In a patient with deep venous thrombosis, plasma concentrations of coagulant and inhibitor proteins were normal except for moderate deficiency of plasminogen. Family studies revealed a similar deficiency in the mother and sister of the propositus. Evaluation of purified plasminogen demonstrated that it functioned normally. The patient represents our only example of plasminogen deficiency in 435 German individuals evaluated with a history of thromboembolism.

Desmopressin Stimulates Parallel Norepinephrine and Tissue Plasminogen Activator Release in Normal Subjects and Patients with Diabetes Mellitus

Desmopressin acetate administration markedly stimulates release of tissue plasminogen activator (t-PA) from vascular endothelial cells. The mechanism for this effect is unknown. Because infusion of epinephrine has been shown to increase t-PA levels, we examined the role of endogenous catecholamine mediation of t-PA release by desmopressin. Intravenous desmopressin acetate (0.3 μg/kg) was infused over 30 min in 9 controls and 11 subjects with diabetes mellitus, a condition associated with abnormalities of the fibrinolytic system. Plasma was collected in the supine, overnight fasted state at 15 min intervals (0-60 min) for measurement of t-PA activity, t-PA antigen and fractionated catecholamines. t-PA activity peaked at 30-45 min and subsequently decreased. The norepinephrine levels paralleled the t-PA activity. t-PA activity increased 10-fold from 0.14 ± .12 to 1.49 ± 0.79 IU/ml (Mean ± SD) and plasma norepinephrine increased 2- fold from 426 ± 90 to 780 ± 292 pg/ml. However, epinephrine and dopamine levels did not change significantly. The response to desmopressin of control and diabetic subjects was not shown to differ and their data were combined. We conclude that desmopressin increases plasma norepinephrine in addition to t-PA and that the parallel time course of change suggests a possible role for norepinephrine in mediating endothelial cell t-PA release.

Pneumococcal vaccines for sickle cell disease

BACKGROUND

People with sickle cell disease are particularly susceptible to pneumococcal infection, which may be fatal. Infants (children aged up to 23 months) are at particularly high risk, but conventional polysaccharide pneumococcal vaccines may be ineffective in this age group. New conjugate pneumococcal vaccines are now available, which may help to reduce the incidence of infection in people with sickle cell disease.

OBJECTIVES

To determine the efficacy of pneumococcal vaccines for reducing morbidity and mortality in people with sickle cell disease.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group trials register, comprising of references identified from comprehensive electronic database searches and hand searching relevant journals and abstract books of conference proceedings. In addition, we contacted relevant pharmaceutical companies and experts in the field.Date of most recent search of Group's trials register: November 2003.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials comparing a polysaccharide or conjugate pneumococcal vaccine regimen with a different regimen or no vaccination in people with sickle cell disease.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected studies for inclusion, extracted data and assessed trial quality.

MAIN RESULTS

Nine trials were identified in the searches and five trials, with a total of 547 participants, met the inclusion criteria. Only one trial reported incidence of pneumococcal infection, and this demonstrated that the polysaccharide pneumococcal vaccine used (PPV14) failed to significantly reduce the risk of infection in children under three years of age, but was associated with only minor adverse events. Three trials of conjugate pneumococcal vaccines found that immune response was increased compared to control groups, including in infants, although clinical outcomes were not measured in these trials.

REVIEWER'S CONCLUSIONS

Previous trials have shown that conjugate pneumococcal vaccines are safe and effective in normal healthy patients, even those under the age of two years. The controlled trials included in this review have demonstrated immunogenicity (the body's response, without which there is no protection) of these vaccines, and observational studies in people with sickle cell disease support these findings. We therefore recommend that conjugate pneumococcal vaccines are used in people with sickle cell disease. Randomised trials in patients with sickle cell disease will be needed to determine the optimal vaccination regimen when further, potentially more effective vaccines become available. Such trials should measure clinical outcomes of effectiveness.

Autoantibody formation in the alloimmunized red blood cell recipient: clinical and laboratory implications

Alloimmunization to erythrocyte antigens is a well-characterized complication in heavily transfused patients. Less well recognized, however, is the frequency of autoantibody formation in these previously alloimmunized patients. The autoantibodies are heterogeneous and of variable clinical significance. We describe the clinical history, laboratory evaluation, diagnosis, and treatment in 4 patients who developed autoantibodies in temporal association with alloantibody formation. In one case, the autoantibody found on routine screening had no clinical significance. In another case, the autoantibody made accurate blood typing and subsequent transfusion exceedingly difficult. Two patients experienced hemolysis as a consequence of the autoantibody. The management of both patients included supportive measures, while one patient required glucocorticosteroids and red blood cell transfusion. We review the published literature concerning autoimmunization in the transfused alloimmunized host. The spectrum of clinical consequences is important for the general practitioner to recognize, as these complications may occur during routine blood transfusions.

Management of a patient with a mechanical aortic valve and antibodies to both thrombin and factor V after repeat exposure to fibrin sealant

We describe a patient who developed a markedly prolonged PT, PTT, and thrombin time 13 days after repeat exposure to fibrin sealant during coronary artery bypass grafting and aortic valve replacement. Evaluation revealed an inhibitor to bovine thrombin that cross-reacted with human thrombin. In addition an inhibitor to human coagulation factor V was identified. Despite coagulation abnormalities there was no evidence of bleeding. Nevertheless, effective anticoagulation was required to minimize the thrombotic complications associated with the patient's prosthetic valve. We elected to take a conservative approach and not utilize pharmacologic anticoagulation until there was diminution in the effect of the acquired inhibitors. We report on our patient's course and review the available literature addressing the management of patients demonstrating inhibitors to blood coagulation factors after repeat exposure to fibrin sealants.

Cloning, expression, sequence analysis, and characterization of streptokinases secreted by porcine and equine isolates of Streptococcus equisimilis

Streptokinases secreted by nonhuman isolates of group C streptococci (Streptococcus equi, S. equisimilis, and S. zooepidemicus) have been shown to bind to different mammalian plasminogens but exhibit preferential plasminogen activity. The streptokinase genes from S. equisimilis strains which activated either equine or porcine plasminogen were cloned, sequenced, and expressed in Escherichia coli. The streptokinase secreted by the equine isolate had little similarity to any known streptokinases secreted by either human or porcine isolates. The streptokinase secreted by the porcine isolate had limited structural and functional similarities to streptokinases secreted by human isolates. Plasminogen activation studies with immobilized (His)(6)-tagged recombinant streptokinases indicated that these recombinant streptokinases interacted with plasminogen in a manner similar to that observed when streptokinase and plasminogen interact in the fluid phase. Analysis of the cleavage products of the streptokinase-plasminogen interaction indicated that human, equine, and porcine plasminogens were all cleaved at the same highly conserved site. The site at which streptokinase was cleaved to form altered streptokinase (Sk*) was also determined. This study confirmed not only the presence of streptokinases in nonhuman S. equisimilis isolates but also that these proteins belong to a family of plasminogen activators more diverse than previously thought.

Species specificity of plasminogen activation and acquisition of surface-associated proteolytic activity by group C streptococci grown in plasma

Our laboratory previously demonstrated that group C streptococcal isolates from humans and horses secrete streptokinases that preferentially activate plasminogens reflecting the origin of the isolates. To analyze the significance of these findings, series of streptokinase-producing Streptococcus equisimilis isolates recovered from humans and horses were examined. Southern blot analysis revealed that chromosomal DNA of the streptococcal isolates from humans reacted exclusively with a skc(hu) probe and that chromosomal DNA of streptococcal isolates from horses reacted preferentially with an skc(eq) probe in a distinct pattern. The streptococcal isolates were examined for the ability to acquire surface-bound plasmin-like activity when grown in the presence of human or equine plasma. Each of eight isolates from humans acquired significant enzymatic activity only when grown in the presence of human plasma, while each of eight isolates from horses acquired activity only when grown in the presence of equine plasma. Analysis of bacterial and host protein requirements indicated critical roles for streptokinase, activatable plasminogen, and fibrinogen. These requirements may explain why certain streptococcal isolates cause disease only in a limited number of mammalian hosts.

Ischemic colitis and acquired resistance to activated protein C in a woman using oral contraceptives

We present the case history of a 22-yr-old woman diagnosed with ischemic colitis associated with the use of oral contraceptives (OC). At the time of her presenting symptoms activated protein C (APC) resistance, a risk factor for thrombosis, was demonstrated. There was no laboratory evidence of inherited thrombophilia; that is, antithrombin III, protein C and protein S levels were normal and the factor V Leiden mutation was not present. The OC were discontinued and the patient's symptoms improved. Subsequent evaluation revealed that the activated protein C resistance had resolved. This case illustrates APC resistance as a potential link between OC use and its known association with ischemic colitis.

Chronic relapsing thrombotic thrombocytopenic purpura and antiphospholipid antibodies: a report of two cases

We report on 2 cases of chronic relapsing thrombotic thrombocytopenic purpura, in which anti-phospholipid antibodies were also found. The first patient was felt to have the anti-phospholipid antibody syndrome, while the second patient had anti-phospholipid antibodies without clinical manifestations of the anti-phospholipid antibody syndrome. We discuss chronic relapsing thrombotic thrombocytopenic purpura and the anti-phospholipid antibody syndrome. Furthermore, we introduce the possibility of an association between chronic relapsing thrombotic thrombocytopenic purpura and the presence of anti-phospholipid antibodies.

Plasminogen activation by invasive human pathogens

In this review the interaction between invasive human pathogens expressing plasmin(ogen) receptors and/or producing plasminogen activators with the human plasmin(ogen) system is described. Evidence is presented for multiple mechanisms by which human pathogens can acquire a surface bound form of plasmin that cannot be regulated by host serpins. The potential importance of these pathways in providing the organisms with the ability to cross tissue barriers is discussed.

The plasmin-binding protein Plr of group A streptococci is identified as glyceraldehyde-3-phosphate dehydrogenase

Group A streptococci bind the serine protease plasmin with high affinity. Previously, a 41 kDa protein was identified as a candidate plasmin receptor protein (Plr) from group A streptococcal strain 64/14. The plr gene encoding Plr was cloned and the deduced amino acid sequence of Plr had significant similarity to glyceraldehyde-3-phosphate dehydrogenases (GAPDHs). In this study we have isolated cytoplasmic GAPDH of streptococcal strain 64/14. This enzyme was examined, on both structural and functional levels, for its relatedness to the Plr of strain 64/14 purified from mutanolysin extract and to recombinant Plr. We report here that no differences were detected between streptococcal Plr and cytoplasmic GAPDH on the basis of antibody reactivity, plasmin-binding activity, GAPDH activity, N-terminal amino acid sequence, peptide map analysis by V8 protease digestion and amino acid composition analysis. Furthermore, the plr gene appears to be present as a single copy in group A streptococci.

Analysis of the interaction of group A streptococci with fibrinogen, streptokinase and plasminogen

Group A streptococci demonstrate a number of distinct ways to interact with the human fibrinolytic system to acquire unregulatable cell-surface enzymatic activity. Interactions between bacteria, fibrinogen, streptokinase and plasminogen resulted in acquisition of cell-associated enzymatic activity that can lyse fibrin clots despite the presence of the major physiological plasmin inhibitor, alpha 2-antiplasmin. Western blot analysis of extracted streptococcal surface proteins suggested that binding of fibrinogen to M or M-related proteins mediated the capture of streptokinase-plasminogen complexes to the bacteria. The enzymatic complex formed by reaction of bacteria with fibrinogen, streptokinase and plasminogen was found to be more stable in human plasma than pre-formed plasmin bound directly to the same bacteria strain.

A role for fibrinogen in the streptokinase-dependent acquisition of plasmin(ogen) by group A streptococci

Acquisition of plasmin(ogen) by group A streptococci occurs by two distinct pathways. In addition to the well-characterized direct interaction of plasmin with cell-surface receptors on group A streptococci, a second pathway dependent on streptokinase and a nonplasminogen factor(s) present in human plasma was identified. The role of streptokinase in the second pathway was not merely as a plasminogen activator, since substitution of the plasminogen activator urokinase did not result in the capture of plasmin(ogen) by bacteria in the presence of plasminogen-depleted plasma. However, if streptokinase was added to plasmin that had been generated by treatment of plasminogen with urokinase, the ability of the bacteria to capture plasmin in the presence of plasminogen-depleted plasma was restored. Fibrinogen present in human plasma was identified as the major factor required for streptokinase-dependent uptake of plasmin(ogen) by group A streptococci.

Characterization of a novel streptokinase produced by Streptococcus equisimilis of non-human origin

Streptokinases are proteins with plasminogen activator activity produced by certain hemolytic streptococci. We previously identified equine streptococcal isolates which produced streptokinases (ESKs) that bound both human and equine plasminogen but only readily activated equine plasminogen (14). This property was exploited to purify a representative ESK produced by Streptococcus equisimilis strain 87-542-W. Affinity chromatography with human plasminogen resulted in the isolation of a M(r) approximately 49,000 molecule with two isoforms. This ESK was subsequently compared to well characterized streptokinases (HSKs) that efficiently activate human plasminogen. Differences in streptokinases were identified in the highly conserved amino-terminal amino acid sequence, peptide maps, and antigenic properties, and these differences were supported by DNA hybridization studies. These results indicate that the family of proteins identified as streptokinases has much greater diversity than previously appreciated.

Capturing host plasmin(ogen): a common mechanism for invasive pathogens?

Plasmin is a potent enzyme that can dissolve blood clots and degrade extracellular matrix proteins. A number of pathogenic bacteria produce plasminogen activators. Many of these organisms can also bind plasmin(ogen) to surface receptors and protect the active enzyme from physiological inhibition. Cell-surface localization of plasmin may be a common mechanism used by bacteria to facilitate movement through normal tissue barriers.

Analysis of plasmin(ogen) acquisition by clinical isolates of group A streptococci incubated in human plasma

Group A streptococci isolated from throat swabs or blood cultures were compared for the expression of plasmin(ogen) receptors. The majority of isolates bound 125I-labeled Lys-plasmin and 125I-labeled Lys-plasminogen while displaying minimal reactivity with 125I-labeled Glu-plasminogen. All streptococcal isolates could acquire surface enzymatic activity when incubated in human plasma but not if the plasma had been depleted of plasminogen. The ability to acquire surface enzymatic activity was limited by the quantity of streptokinase in the reaction mixture. There was no statistically significant difference between group A streptococci isolated from throat swabs and those from blood cultures with respect to their interaction with components of the fibrinolytic system in human plasma. However, these isolates could be divided into two groups based on their ability to acquire surface enzymatic activity when incubated in plasma with exogenous streptokinase. Surprisingly, the acquisition of surface enzymatic activity when incubated in plasma containing streptokinase was not always correlated with the plasmin(ogen) binding capacity determined by direct binding of radiolabeled ligands. Analysis of this phenomenon suggests that group A streptococci can use diverse mechanisms to acquire plasmin(ogen)-dependent enzymatic activity.

Cloning, sequence analysis, and expression in Escherichia coli of a streptococcal plasmin receptor

Plasmin(ogen) receptors are expressed by many gram-positive and gram-negative bacteria. We previously isolated a plasmin receptor from a pathogenic group A streptococcal strain (C. C. Broder, R. Lottenberg, G. O. von Mering, K. H. Johnston, and M. D. P. Boyle, J. Biol. Chem. 266:4922-4928, 1991). The gene encoding this plasmin receptor, plr, was isolated from a lambda gt11 library of chromosomal DNA from group A streptococcal strain 64/14 by screening plaques with antibodies raised against the purified streptococcal plasmin receptor protein. The gene was subcloned by using a low-copy-number plasmid and stably expressed in Escherichia coli, resulting in the production of an immunoreactive and functional receptor protein. The DNA sequence of the gene contained an open reading frame encoding 335 amino acids with a predicted molecular weight of 35,787. Upstream of the open reading frame, putative promoter and ribosomal binding site sequences were identified. The experimentally derived amino acid sequences of the N terminus and three cyanogen bromide fragments of the purified streptococcal plasmin receptor protein corresponded to the predicted sequence encoded by plr. The deduced amino acid sequence for the plasmin receptor protein revealed significant similarity (39 to 54% identical amino acid residues) to glyceraldehyde 3-phosphate dehydrogenases.

Streptokinase-producing streptococci grown in human plasma acquire unregulated cell-associated plasmin activity

Group A streptococci grown in the presence of human plasma generated plasmin from plasminogen and captured the functional enzyme to a specific cell-surface receptor. Bacteria-bound plasmin was not regulated by alpha 2-antiplasmin present in the medium. The ability of the bacteria to acquire cell-associated plasmin activity was dependent on both the presence of plasminogen in the culture medium and the production of a bacterial plasminogen activator, streptokinase. The ability of group A streptococci to produce a plasminogen activator and capture resulting plasmin in an unregulatable form could provide the organism with a mechanism for invasion of normal tissue barriers.

Identification of two type IIa IgG-binding proteins expressed by a single group A streptococcus

Functional heterogeneity associated with Ig-binding proteins expressed by group A streptococci is well documented. In this study we have demonstrated that treatment of group A streptococcal isolate 64/14 with CNBr resulted in the solubilization of two different sized proteins that displayed identical functional reactivity with human IgG1, IgG2, and IgG4 (characteristics of a type IIa binding protein). Monospecific polyclonal antibodies to each form of type IIa molecule were prepared and no antigenic cross-reactivity between the two m.w. forms of type IIa binding protein could be detected. The smaller m.w. protein was shown to be identical or closely related to the recombinant type IIa protein cloned from strain CS110. These studies provide further evidence for the heterogeneity of type II Ig-binding proteins expressed by pathogenic group A streptococci.

Identification of two type IIa IgG-binding proteins expressed by a single group A streptococcus

Functional heterogeneity associated with Ig-binding proteins expressed by group A streptococci is well documented. In this study we have demonstrated that treatment of group A streptococcal isolate 64/14 with CNBr resulted in the solubilization of two different sized proteins that displayed identical functional reactivity with human IgG1, IgG2, and IgG4 (characteristics of a type IIa binding protein). Monospecific polyclonal antibodies to each form of type IIa molecule were prepared and no antigenic cross-reactivity between the two m.w. forms of type IIa binding protein could be detected. The smaller m.w. protein was shown to be identical or closely related to the recombinant type IIa protein cloned from strain CS110. These studies provide further evidence for the heterogeneity of type II Ig-binding proteins expressed by pathogenic group A streptococci.

Streptokinases produced by pathogenic group C streptococci demonstrate species-specific plasminogen activation

The species specificities of plasminogen activation and binding of plasmin by pathogenic group C streptococci isolated from humans, horses, and pigs were examined. Of 56 streptococcal isolates, 52 elaborated plasminogen activator activity and 49 of these had specificity for plasminogen of the homologous host. Analysis of supernatants from 13 isolates indicated that the plasminogen activator activity resulted from secreted streptokinases. These 13 streptokinases were antigenically related and bound all three plasminogens, indicating that the binding recognition sites were conserved despite the observed species-specific activation. In addition, all group C isolates tested demonstrated surface receptors that bound human, equine, and porcine plasmin. Species-specific plasminogen activation may be an early step in events resulting in infection and may account for the species preference of certain streptococci.

Immunological and molecular characterization of plasminogen activator inhibitors 1 and 2 in baboon (Papio anubis) placental tissues

Two major plasminogen activator inhibitors (PAI-1 and PAI-2) increase in the peripheral circulation during pregnancy in humans. PAI-1 is of vascular endothelial origin whereas PAI-2 is produced primarily by human placental tissues. This study was undertaken to determine a) if PAI-1 and PAI-2 are also present in the baboon and b) their association with pregnancy. Citrated plasma was obtained from pregnant baboons sequentially at 15 +/- 3-day intervals between Days 30 and 140 of pregnancy. PAI activity increased significantly (p less than 0.05) at Day 120 (15.3 IU/ml) and 140 (21.8 IU/ml) of gestation and returned to baseline (2.6 IU/ml) 48 h post cesarean section. Placental tissues obtained at cesarean section during the third trimester were either placed in explant culture, fixed for immunocytochemistry, or frozen for RNA extraction. Western blot analysis of tissue culture media (TCM) indicated that the polyclonal antibody to PAI-1 reacted with a major band (Mr 47 000) in TCM from placental tissues while the PAI-2 antibody reacted primarily with a doublet (Mr 67 000 and 69 000) in these same media. PAI-1 was immunocytochemically localized primarily in the chorioamniotic tissue (CAM-D) and PAI-2 was found predominantly in placental villi. Slot blot hybridization with cDNAs to PAI-1 and PAI-2 indicated that the mRNA for PAI-2 was found primarily in placental villi, whereas the mRNA for PAI-1 was present in all three tissue compartments.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of a prokaryotic plasmin receptor. Relationship to a plasminogen activator produced by the same micro-organism

Plasminogen receptors have been identified on the surface of a number of prokaryotic and eukaryotic cells. A receptor demonstrating high affinity for plasmin with minimal reactivity with the native zymogen Glu-plasminogen has been identified on the surface of certain group A streptococci. In this study the group A streptococcal plasmin receptor has been solubilized and purified to homogeneity. The isolated protein was an Mr approximately 41,000 molecule which retained its ability to bind plasmin following solubilization and affinity purification on a column of enzymatically inactivated human plasmin. The isolated plasmin receptor was compared functionally, antigenically, and physicochemically to the secreted plasminogen activator, streptokinase, produced by the same organism. The Mr approximately 41,000 surface plasmin receptor was shown to be functionally and antigenically distinct from the Mr approximately 48,000 streptokinase molecule produced by the same strain and lacked any plasminogen activator activity. The streptokinase molecule produced by this strain was shown to be closely related to the plasminogen activator protein secreted by other group A and C streptococci. This study represents the first report of the isolation of a plasmin receptor, either prokaryotic or eukaryotic, with functional activity.

Fibrinolytic capacity following stimulation with desmopressin acetate in patients with diabetes mellitus

Tissue plasminogen activator (t-PA), tissue plasminogen activator inhibitor, (PAI), and von Willebrand factor (vWF) were measured in 30 diabetics and 17 control subjects. These studies were performed to clarify the role of obesity in causing abnormalities of the fibrinolytic system in diabetics. The t-PA antigen response measured after the infusion of desmopressin acetate (DDAVP) was similar in all groups. Peak responses to DDAVP for controls, type I diabetics, and type II diabetics were 21.2 +/- 9.5 ng/mL, 27.5 +/- 9.0 ng/mL, and 28.8 +/- 11.0 ng/mL (NS), respectively. These responses did not correlate with the body mass index (BMI) or any other of the indices examined. A significant decrease of t-PA activity as contrasted with t-PA antigen following DDAVP occurred in type II diabetics only. The decrease of t-PA activity strongly correlated with greater basal levels of plasminogen activator inhibitor in these same subjects. The plasma level of plasminogen activator inhibitor correlated with BMI but with no other index examined. In contrast to t-PA activity and PAI, vWF responses to DDAVP inversely correlated to basal vWF concentration in all groups. Basal concentrations of vWF were increased in both type I and II diabetics and showed no relationship to degree of obesity. In summary, these results suggest that type II diabetic subjects have decreased t-PA activity, which is best explained by increased levels of PAI. The increased PAI appears related to obesity and not diabetes per se.

Mapping of the human plasmin domain recognized by the unique plasmin receptor of group A streptococci

A high-affinity surface receptor for human plasmin has been reported on certain group A streptococci. To map the region of the plasmin molecule that binds to the bacterial receptor, isolated domains of plasmin were tested for their ability to inhibit the binding of intact radiolabeled plasmin to receptor-positive bacteria. Complete inhibition of binding of labeled plasmin to bacteria by isolated heavy chains was achieved, but this inhibition was not as efficient on a molar basis when compared with that of unlabeled plasmin. By contrast, a conformationally altered form of native plasminogen was found to bind to bacteria and was as efficient a competitive inhibitor as intact plasmin was. The results of this study indicate that the selective binding of human plasmin to a group A streptococcus is dependent on structures present in the conformationally altered form of native plasminogen or plasmin that are not found on the native zymogen, the plasminogen with NH2-terminal glutamic acid.

Group A streptococci bind human plasmin but not other structurally related proteins

Certain group A streptococci are known to possess a receptor for the human enzyme plasmin. Plasmin is a member of a super gene family that includes other serine proteases and kringle containing proteins. In this study we have examined the interaction of a group A streptococcus with structurally related proteins, including plasmin, glu-plasminogen, tissue plasminogen activator, kallikrein, factor XII, prothrombin, thrombin, trypsin, and urokinase. Our studies indicate that only the key fibrinolytic enzyme, plasmin, demonstrates significant binding activity to the group A streptococcus.

Familial protein S deficiency with a variant protein S molecule in plasma and platelets

A protein S deficient family presenting a variant protein S molecule in plasma and platelets is described. The propositus, age 20, and two brothers suffered from venous thrombotic disease. The propositus, the only family member studied while taking oral anticoagulants, had a protein S antigen (ag) level of 17% and undetectable activity. As demonstrated by immunoblotting both the propositus and one clinically affected brother (42% ag, 7% activity) presented variant protein S molecules of 65,000 molecular weight (mol wt) while the other clinically affected brother (64% ag, 11% activity) had only protein S with normal electrophoretic mobility of 70,000 mol wt. The mother had normal protein S levels (93% ag, 100% activity) but had both normal and variant protein S molecules and based on her functional protein S data a normal anticoagulant activity of the variant molecule is suggested. One asymptomatic but protein S deficient sister (68% ag, 9% activity) as well as the asymptomatic protein S deficient father (59% ag, 10% activity) had only protein S molecules of 70,000 mol wt. The variant protein S bound to C4b-binding protein in plasma, and differed from normal protein S in carbohydrate content. Platelets of each family member contained the same immunoblotting pattern of normal and variant protein S forms as found in plasma, consistent with the hypothesis that protein S gene expression involves codominant expression of two alleles that is similar in cells that control the synthesis of both platelet and plasma forms of protein S.

Procoagulant synthesis by exudate and bone marrow-derived murine macrophages

Murine exudate macrophages elicited by different stimuli and bone marrow-derived macrophages were studied for their capacity to synthesize factor VII and tissue factor in a basal state and on stimulation with endotoxin (LPS). Cells elicited by different stimuli varied in their production of both factors. Thioglycollate-elicited cells generally made more, but not significantly more, tissue factor in response to endotoxin than cells elicited with periodate or streptococci. Cells elicited with proteose-peptone, fetal calf serum (FCS), or LPS produced less or very little tissue factor. Thioglycollate-elicited cells and cells elicited with streptococci or proteose-peptone consistently made more factor VII than cells elicited with periodate, FCS, and LPS. Bone marrow-derived macrophages were responsive to LPS by the production of tissue factor by the fifth day of culture, and this rose to a maximum by day 10. The maximal production of factor VII occurred on day 5 of culture and declined with longer cultivation. Factor VII production was not enhanced by LPS, and prolonged cultivation in the presence of LPS turned off the synthesis of both tissue factor and factor VII. We conclude that exudate cells are heterogeneous in the production of coagulant factors and that the production of these factors varies with the maturity of the cells. In addition, the production of the tissue factor and the factor VII were not necessarily expressed in a coordinate fashion.

Characterization of the interaction of human plasmin with its specific receptor on a group A streptococcus

Certain Group A beta-hemolytic streptococci express a receptor that is capable of specifically binding the human plasma protease plasmin. Once bound, plasmin remains enzymatically active and is unregulated by its naturally occurring inhibitor alpha-2-antiplasmin (Lottenberg, R., C. C. Broder and M. D. P. Boyle, 1987. Infect. Immun. 55: 1914-1918). In this study certain characteristics of the interaction between plasmin and the receptor expressed on a group A beta-hemolytic streptococcus, strain 64/14, were examined. Binding occurred optimally at physiologic pH and ionic strength. The KD was 5 x 10(-11) M and there were approximately 800 receptors per bacterium. Mouse passage of strain 64 had no significant effect on the KD of the receptor. Binding of plasmin to the bacteria was inhibited by lysine and epsilon-aminocaproic acid in a concentration dependent manner. Similarly these amino acids would displace pre-bound plasmin from the bacteria. These findings suggest a role for plasmin's high affinity lysine binding site in the interaction of plasmin with the bacteria.

Congenital deficiency of plasminogen and its relationship to venous thrombosis

In a patient with deep venous thrombosis, plasma concentrations of coagulant and inhibitor proteins were normal except for moderate deficiency of plasminogen. Family studies revealed a similar deficiency in the mother and sister of the propositus. Evaluation of purified plasminogen demonstrated that it functioned normally. The patient represents our only example of plasminogen deficiency in 435 German individuals evaluated with a history of thromboembolism.

Desmopressin stimulates parallel norepinephrine and tissue plasminogen activator release in normal subjects and patients with diabetes mellitus

Desmopressin acetate administration markedly stimulates release of tissue plasminogen activator (t-PA) from vascular endothelial cells. The mechanism for this effect is unknown. Because infusion of epinephrine has been shown to increase t-PA levels, we examined the role of endogenous catecholamine mediation of t-PA release by desmopressin. Intravenous desmopressin acetate (0.3 micrograms/kg) was infused over 30 min in 9 controls and 11 subjects with diabetes mellitus, a condition associated with abnormalities of the fibrinolytic system. Plasma was collected in the supine, overnight fasted state at 15 min intervals (0-60 min) for measurement of t-PA activity, t-PA antigen and fractionated catecholamines. t-PA activity peaked at 30-45 min and subsequently decreased. The norepinephrine levels paralleled the t-PA activity. t-PA activity increased 10-fold from 0.14 +/- .12 to 1.49 +/- 0.79 IU/ml (Mean +/- SD) and plasma norepinephrine increased 2-fold from 426 +/- 90 to 780 +/- 292 pg/ml. However, epinephrine and dopamine levels did not change significantly. The response to desmopressin of control and diabetic subjects was not shown to differ and their data were combined. We conclude that desmopressin increases plasma norepinephrine in addition to t-PA and that the parallel time course of change suggests a possible role for norepinephrine in mediating endothelial cell t-PA release.

Enzyme-labeled type III bacterial Fc receptors. A versatile tracer for immunoassay

The type III bacterial Fc receptor isolated form a group C streptococcus has been conjugated to alkaline phosphatase and used as a tracer in a variety of direct and indirect immunoassays. These immunoassays have utilized specific antibodies prepared in species whose immunoglobulins are poorly reactive with the type I Fc receptor, staphylococcal protein A. The value of the type III Fc receptor as a tracer for immunoassays utilizing antibodies produced in sheep and goats is documented.

Aprotinin inhibits urokinase but not tissue-type plasminogen activator

The protease inhibitor, aprotinin, has been examined for its ability to inhibit urokinase and tissue-type plasminogen activators at pH 7.4 in assays utilizing pyroGlu-Gly-Arg-p-nitroanilide and H-D-Ile-Pro-Arg-p-nitroanilide as substrates, respectively. Aprotinin inhibited both two-chain low molecular weight urokinase and the high molecular weight form of the enzyme in a competitive manner with a similar Ki (27 microM). There was no observable inhibition of tissue-type plasminogen activators at aprotinin concentrations up to 500 microM. These findings suggest that sensitivity to inhibition by aprotinin could be used to distinguish tissue-type and urokinase-type plasminogen activators.

Identification of a specific receptor for plasmin on a group A streptococcus

Certain group A streptococci demonstrate surface receptors that bind selectively to the key fibrinolytic enzyme, plasmin. These bacteria show no reactivity with the zymogen protein plasminogen or with other serine class proteases, such as trypsin or urokinase. Bacterium-bound plasmin retains its ability to cleave synthetic substrates and its ability to hydrolyze a fibrin clot. The bacterium-bound plasmin is not effectively regulated by its physiological regulator, alpha 2-plasmin inhibitor. This study is the first report of a bacterium-associated receptor for plasmin.

Acquired hemophilia. A natural history study of 16 patients with factor VIII inhibitors receiving little or no therapy

Rarely, a patient develops an antibody against factor VIII coagulant activity. The resultant hemorrhagic diathesis is clinically distinct from inherited hemophilia, being characterized by few hemarthroses but frequent skin and other soft-tissue hematomas. Hematuria may be troublesome. These patients represent therapeutic challenges. This study is one institution's results with 16 such patients followed up over an average of 31 months (range, four to 120 months; median, 19 months). It describes the largest group from a single institution receiving essentially no immunosuppressive agents, yet has one of the better overall results. Two patients experienced fatal hemorrhage and five patients underwent spontaneous remission. Long-term survival is not incompatible with persistence of the inhibitor. We conclude that this hemorrhagic diathesis is clinically distinct, less fatal than usually perceived, and may undergo spontaneous remission. Clearly, there is no mandate for any particular therapeutic regimen, such as immunosuppression, in the attempt to rid the patient of the antibody.

Clinical efficacy of desmopressin acetate for hemostatic control in patients with primary platelet disorders undergoing surgery

Desmopressin acetate (DDAVP) is efficacious in patients with von Willebrand's disease. It additionally appears to have value in patients with uremic or aspirin-induced platelet dysfunction. We report here three patients with primary platelet defects who had previously experienced grossly inadequate hemostasis to whom we administered DDAVP. Each successfully underwent surgical procedures with DDAVP as the only hemostatic agent. Although the mechanism of these salutary effects is unclear, DDAVP may exert an influence directly on the endothelium independent of correcting abnormalities of the factor VIII:von Willebrand complex associated with von Willebrand's disease.

The rapid inhibition of urokinase by plasma from pregnant women at risk for abruptio placenta

Rapid inhibition of urokinase in plasma obtained from women in the third trimester of pregnancy was assessed by the addition of 75 IU urokinase per ml plasma, and measurement of residual urokinase activity with PyroGlu-Gly-Arg-pNA after 5 minutes incubation at 37 degrees C. The urokinase inhibitory capacity was markedly increased for the pregnant women compared to non-pregnant controls. Alpha 1-antitrypsin, alpha 2-macroglobulin and alpha 2-antiplasmin did not account for the activity. Inhibition was higher for women with multiple gestations or macrosomia (n = 11) compared to normal pregnant women (n = 35) suggesting that the placenta contributes significantly to the measured activity. Inhibition was lower for women with hypertension (n = 33) compared to the normal pregnant women. Although the etiology for this difference is unclear, the decreased inhibitory activity may contribute to the increased risk for placental abruption that is observed for this group of women.

The action of factor Xa on peptide p-nitroanilide substrates: substrate selectivity and examination of hydrolysis with different reaction conditions

Kinetic parameters for the action of bovine Factor Xa (EC 3.4.21.22) on 25 commercially available peptide p-nitroanilides have been determined. The selectivity constant, kc/Km, ranges from 1.5 X 10(1) to 2 X 10(6) M-1 X s-1 for the poorest and the best substates, respectively. The best substrates for Factor Xa were identified as those with arginine in the P1 position, and glycine in the P2 position. Quantitative distinction between lysine and arginine in the P1 position and other amino acids in the P2-P4 positions of the substrate is reported from the changes in the kinetic parameters for substrates differing in only a single amino acid in these positions. Effect of NaCl and CaCl2 concentrations and temperature on the action of Factor Xa on selected substrates have been assessed. Km values for Factor Xa hydrolysis of most substrates are greater than 100 microM. Solubility of the substrates consequently restricts measurements of reaction velocities to concentrations lower than desirable for optimally determining kc. Comparison of these kinetic parameters for Factor Xa with those of thrombin (Lottenberg, R., Hall, J.A., Blinder, M., Binder, E. and Jackson, C.M. (1983) Biochim. Biophys. Acta 742,539-557) for these same substrates indicates that the greater hydrolytic efficiency of thrombin is due primarily to lower Km values.

Recurring thromboembolic disease and pulmonary hypertension associated with severe hypoplasminogenemia

In a patient with pulmonary hypertension and a history of recurrent venous thrombosis, plasma concentrations of all known coagulant and inhibitor proteins were normal except for severe deficiency of plasminogen. Repeated analyses showed the circulating plasma plasminogen level to be 30% of normal by either functional or immunologic methods. We sought evidence for either increased activation of plasminogen or for dysplasminogen. There was no evidence for the former. Purified plasminogen studies disclosed a normal number of active sites and normal activation. Generated plasmin had normal catalytic activity. Isoelectric focusing disclosed normal distribution of isoforms. Affinity chromatography with lysine-sepharose showed the presence of the two variant forms; however, an increased proportion of the protein eluted in the first peak. Danazol administration induced an increase in circulating plasminogen, but the differences in affinity chromatography elution profile remained. We conclude that this patient has a deficiency of normally functioning plasminogen, probably due to decreased synthesis.

The syndrome of idiopathic myelofibrosis. A clinicopathologic review with emphasis on the prognostic variables predicting survival

We describe here a series of 88 consecutive patients with bone marrow fibrosis. Primary causes for the fibrosis were discovered in 26% of the cases shortly after the initial diagnosis. Pathology review of the remaining cases revealed an 8% incidence of "hairy cell leukemia" that had escaped detection originally. The remaining cases, characterized as having "unexplained bone marrow fibrosis" or "idiopathic myelofibrosis," are the subject of this study. The clinical and laboratory findings are compared to those reported in previous series of selected cases with similar features in which patients were diagnosed as having "agnogenic myeloid metaplasia," "myelosclerosis," or "myelofibrosis." A brief summary of the treatment modalities used, and the clinical course and outcome of these patients are also presented. There was a marked variability in the clinical severity of the disease and in the survival of these patients. A detailed statistical analysis of 40 variables at the time of initial diagnosis showed that the factors that best predicted a poor survival were unexplained fever, weight loss, night sweats, anemia and thrombocytopenia. On the other hand, the size of the spleen or of the liver, the degree of immaturity of the peripheral blood white cells, and the degree of fibrosis or cellularity in the bone marrow biopsy were of no detectable prognostic significance. These findings suggest that in patients with unexplained fibrosis of the bone marrow (the syndrome of idiopathic myelofibrosis) a poor prognosis is not a direct consequence of the marrow fibrosis or the associated extramedullary hematopoiesis, but rather is related to the presence and/or the severity of some unexplained primary marrow defect, which is also often associated with the nonspecific symptoms of a systemic illness.

The action of thrombin on peptide p-nitroanilide substrates. Substrate selectivity and examination of hydrolysis under different reaction conditions

Kinetic parameters for the action of bovine alpha-thrombin on 24 commercially available peptide p-nitroanilides have been determined. The selectivity constant, kcat/Km, ranges from 3.3 X 10(1) to 1.1 X 10(8) M-1 X S-1 for the poorest and the best substrates, respectively. The best substrates for thrombin were identified as those with arginine in the P1 position, proline or a proline homolog in the P2 position, and an apolar amino acid in the P3 position. Quantitative distinction between lysine and arginine in the P1 position and other amino acids in the P2-P4 positions of the substrate is reported from the changes in the kinetic parameters for substrates differing in only a single amino acid in these positions. Effects of NaCl, CaCl2 and poly(ethylene glycol) concentrations, pH and temperature on the action of thrombin on selected substrates have been assessed. A source of large systematic error in thrombin concentration estimates was identified as resulting from adsorption losses. These losses were eliminated by inclusion of poly(ethylene glycol) in dilution and reaction buffers.

Solution composition dependent variation in extinction coefficients for p-nitroaniline

The dependence of the extinction coefficients for para-nitroaniline on solution composition has been investigated. The p-nitroaniline absorption spectrum is red-shifted with increasing ionic strength, with the consequence that the extinction coefficients at fixed wavelengths may vary significantly. The isosbestic wavelength for peptide p-nitroanilide/p-nitroaniline mixtures is similarly shifted. Poly(ethylene glycol) and bovine albumin, two additives frequently employed to eliminate enzyme loss from adsorption to cuvette and dilution vessel surfaces, also induce shifts in the p-nitroaniline spectrum. The use of a difference extinction coefficient at 381 nm, the p-nitroaniline maximum wavelength, is proposed to minimize the error resulting from solution composition dependent spectral shifts.

The action of thrombin on peptide p-nitroanilide substrates: hydrolysis of Tos-Gly-Pro-Arg-pNA and D-Phe-Pip-Arg-pNA by human alpha and gamma and bovine alpha and beta-thrombins

Human and bovine alpha-thrombins (greater than 90% alpha form) with high fibrinogen clotting activities (approximately 3,000 U.S. units/mg protein) exhibit similar Michaelis menten kinetics with the p-nitroanilide tripeptide substrates Tos-Gly-Pro-arg-pNA (Chromozym-TH) and D-Phe-Pip-Arg-pNA (S-2238). The kinetic parameters at I = 0.11 M, 25 degrees C, pH 7.8 are: (Km = 4.18 +/- 0.22 and 3.61 +/- 0.15 microM; kcat = 127 +/- 8 and 100 +/- 1 s-1) for Chromozym TH and (Km = 1.33 +/- 0.07 and 1.50 +/- 0.10 microM; kcat = 91.4 +/- 1.8 and 98.0 +/- 0.5 s-1) for S-2238 for the human and bovine enzymes, respectively. Unlike the native enzyme forms, their "non-clotting" terminal degradative forms, human gamma-thrombin (approximately 5 units/mg) and bovine beta-thrombin (approximately 200 units/mg), give increased values for these parameters (km = 14.3 +/- 2.4 and 14.4 +/- 2.2 microM; kcat = 160 +/- 9 and 124 +/- 6 s-1) for Chromozym-TH; and (Km = 2.50 +/- 0.36 and 2.99 +/- 0.33 microM; kcat = 106 +/- 3 and 106 +/- 3 s-1) for S-2238. Based on these parameters, 50% degradation of human or bovine alpha-thrombins can be calculated to produce relatively small errors in the kinetic measurement of total thrombin concentrations (maximally 9% and 7% for Chromozym-TH; 7% and 3% for S-2238, respectively) if the kinetic parameters for all alpha forms are erroneously used and assays are at 150 microM substrate. This is in contrast to the large errors inherent in clotting activity measurements on thrombin mixtures. Incorporation of 1 mg/ml of polyethylene glycol 6,000 into assay solutions eliminates systematic errors otherwise caused by thrombin adsorption to surfaces and enables thrombin to be accurately assayed at concentrations less than 0.1 nM or 0.01 clotting unit/ml of alpha-thrombin.

Iron studies in hemophilia

Although iron deficiency is not recognized as a usual complication of hemophilia, we questioned whether intermittent occult loss of blood in urine or stool might predispose hemophiliacs to chronic iron deficiency. Seven men with factor VII and one with factor IX deficiency were studied. Blood studied, bone marrow aspirates, urine and stool samples, and ferrokinetics with total-body counting up to five months were examined. These data showed no excessive loss of blood during the study period; however, marrow iron stores were decidedly decreased, being absent in four subjects. We suggest that in some hemophiliacs, iron deposits in tissues such as synovial membranes may form a high proportion of the body's total iron stores.