Spreading of diblock copolymer droplets: a probe of polymer micro-rheology.

We present an experimental study of the spreading dynamics of symmetric diblock copolymer droplets above and below the order-disorder transition. Disordered diblock droplets are found to spread as a homopolymer and follow Tanner's law (the radius grows as R approximately t(m), where t is time and m = 1/10). However, droplets that are in the ordered phase are found to be frustrated by the imposed lamellar microstructure. This frustration is likely at the root of the observed deviation from Tanner's law: droplet spreading has a much slower power law (m approximately 0.05+/-0.01). We show that the different spreading dynamics can be reconciled with conventional theory if a strain-rate-dependent viscosity is taken into account.

Kinetics of layer hopping in a diblock copolymer lamellar phase.

In the ordered state, symmetric diblock copolymers self-assemble into an anisotropic lamellar morphology. The equilibrium thickness of the lamellae is the result of a delicate balance between enthalpic and entropic energies, which can be tuned by controlling the temperature. Here we devise a simple yet powerful method of detecting tiny changes in the lamellar thickness using optical microscopy. From such measurements we characterize the enthalpic interaction as well as the kinetics of molecules as they hop from one layer to the next in order to adjust the lamellar thickness in response to a temperature jump. The resolution of the measurements facilitate a direct comparison to predictions from self-consistent field theory.

Fibrinolytic changes in a patient with toxic shock syndrome; release of active u-PA.

OBJECTIVE: Definition of the changes in the activators of plasminogen, u-PA and t-PA, and examination of the possible generation of plasmin in the circulation in overwhelming sepsis. DESIGN: Serial blood analysis starting 4 h after development of symptoms of toxic shock syndrome. SETTING: Intensive care unit. PATIENT: A previously healthy woman underwent endometrial ablation and rapidly thereafter developed staphylococcal toxic shock syndrome with organ failure. MEASUREMENT AND RESULT: t-PA, PAI-1, t-PA-PAI-1 complexes, plasminogen, fibrinogen and plasmin-alpha 2-antiplasmin complexes were measured serially by ELISA and free u-PA by SDS-PAGE with zymography. The onset of symptoms was accompanied by a rise of t-PA antigen-followed rapidly by PAI-1 antigen. Plasmin-alpha 2-antiplasmin complex was generated in large amounts but disappeared within hours. From day 3, free u-PA was detectable in the circulation without plasmin generation. CONCLUSION: Despite the sustained presence of active u-PA in the circulation and of t-PA antigen at the onset of symptoms, plasmin-alpha 2-antiplasmin generation was largely suppressed by high levels of PAI-1. The suppression of plasmin generation by u-PA and t-PA may ensure the persistence of fibrin in the microcirculation and so contribute to organ failure.

Tumour cell u-PA as a cause of fibrinolytic bleeding in metastatic disease.

Tumour cells may express urokinase type plasminogen activator (u-PA). This may influence the invasive properties of the cells but has seldom been implicated in production of a systemic bleeding state. Two patients are described in whom severe bleeding occurred in association with disseminated malignancies. Thrombin generation was little disturbed and platelet numbers were insufficient to account for the bleeding. Florid plasmin generation was evident in the circulation and the fibrinolytic inhibitor tranexamic acid controlled the bleeding well. Free active u-PA was demonstrated in the circulation and u-PA antigen on the malignant cells which invaded the marrow of one of the patients. Tumour cell u-PA may occasionally be responsible for a bleeding state.

Proteins of the fibrinolytic system in human thrombi.

The proteins of fibrinolysis have been quantified in human thrombi, to assess the balance between plasminogen activators and their major inhibitor PAI-1. The relative roles of PAI-1 and alpha 2-AP were also examined since we have previously shown that both platelet PAI-1 and plasma alpha 2-AP are important determinants of clot lysis in vitro. Extracts and sections were prepared from human thrombi for quantitative immunoassay and immunohistochemical staining respectively. PAI-1 and alpha 2-AP were present at high concentrations. Levels of t-PA and t-PA-PAI-1 complex were relatively low. Staining confirmed the presence of abundant PAI-1, associated primarily with platelet material within the thrombus and also with fibrin. Staining for alpha 2-AP was also intense and demonstrated strong association with fibrin. The alpha 2-AP concentration was similar to its high plasma concentration, whereas PAI-1 levels were up to 30 times greater than that in circulating blood, suggesting that active recruitment of platelets contributes to the high PAI-1 concentration in thrombi.

Tissue plasminogen activator, plasminogen activator inhibitors, and activator-inhibitor complex in liver disease.

AIMS: To identify the relative contribution of plasminogen activators, particularly tissue plasminogen activator (t-PA) and specific plasminogen activator inhibitors (PAI-1, PAI-2), to the fibrinolytic changes associated with various types of liver disease or severe chemical and physical damage to the liver. METHODS: Platelet rich (PRP) and platelet poor plasma (PFP) from patients with alcoholic cirrhosis, primary biliary cirrhosis, hepatic malignancy, or paracetamol overdose, or who were undergoing partial hepatectomy or liver transplantation, were assayed for t-PA, PAI-1, t-PA-PAI-1 complex and PAI-2 antigen values using specific enzyme linked immunosorbent assays (ELISAs) developed in this laboratory. RESULTS: Appreciable increases in the plasma concentration of t-PA, PAI-1, and t-PA-PAI-1 were seen in patients with alcoholic cirrhosis, primary biliary cirrhosis, and hepatic malignancy. Liver damage due to paracetamol overdose and partial hepatectomy both resulted in a striking increase in plasma PAI-1 concentration, although concentrations of t-PA and t-PA-PAI-1 complex were less affected. Concentrations of t-PA, PAI-1, and t-PA-PAI-1 complex returned to near normal values after successful liver transplantation in a patient with chronic active hepatitis. PAI-2 was also detected in several patients with chronic liver disorders. CONCLUSIONS: Haemorrhage due to fibrinolytic bleeding is commonly associated with liver disease. The patients studied here all had appreciable increases in circulating t-PA antigen concentrations. This was associated with increased concentrations of PAI-1 antigen and t-PA-PAI-1 complex and the balance between activator and inhibitor did not result in systemic plasmin generation. Reduced PAI-1 activity in cirrhosis or a critical difference in the ratio of t-PA to PAI-1 concentrations may explain the enhanced plasminogen activator activity previously noted in cirrhosis but not metastatic disease. Reduced hepatic clearance of t-PA and t-PA-PAI-1 complex due to impaired liver function may account for increased concentrations of free and complexed t-PA.

Distribution of plasminogen activator inhibitor in normal liver, cirrhotic liver, and liver with metastases.

AIMS: To examine the distribution of PAI-1 antigen in normal and cirrhotic liver and liver with metastases. METHODS: Sections of normal and cirrhotic liver and liver with metastases were stained using the alkaline phosphatase antialkaline phosphatase (APAAP) technique and monoclonal antibody specific for plasminogen activator inhibitor (PAI-1). RESULTS: PAI-1 antigen was identified as discrete granules in the cytoplasm of hepatocytes in normal liver, particularly around portal tracts and central veins of the liver lobule. In cirrhotic liver a striking reduction of PAI-1 antigen was noted. In liver with metastases increased amounts of PAI-1 antigen were concentrated in hepatocytes around the margins of malignant deposits. CONCLUSIONS: Cirrhotic liver contains considerably less PAI-1 antigen than does normal liver, despite raised plasma concentrations of PAI-1. This may reflect release of hepatic PAI-1 into the circulation or decreased clearance of PAI-1 from the plasma. Secondary malignant deposits in the liver seem to stimulate production of PAI-1 in adjacent hepatocytes. This may influence the invasive process and may contribute to the thrombotic tendency associated with malignancy.

The roles of alpha 2-antiplasmin and plasminogen activator inhibitor 1 (PAI-1) in the inhibition of clot lysis.

The relative importance of the two major inhibitors of fibrinolysis, alpha 2-antiplasmin (alpha 2-AP) and plasminogen activator inhibitor (PAI-1), were investigated using a simple microtitre plate system to study fibrin clot lysis in vitro. Cross-linked fibrin clots contained plasminogen and tissue plasminogen activator (t-PA) at concentrations close to physiological. Purified alpha 2-AP and PAI-1 caused dose-dependent inhibition. All the inhibition due to normal plasma, either platelet-rich or poor, was neutralised only by antibodies to alpha 2-AP. Isolated platelets, at a final concentration similar to that in blood, 2.5 x 10(8)/ml, markedly inhibited clot lysis. This inhibition was neutralised only by antibodies to PAI-1. At the normal circulating ratio of plasma to platelets, alpha 2-AP was the dominant inhibitor. When the platelet:plasma ratio was raised some 20-fold, platelet PAI-1 provided a significant contribution. High local concentrations of PAI-1 do occur in thrombi in vivo, indicating a role for PAI-1, complementary to that of alpha 2-AP, in such situations.

Complexing of tissue plasminogen activator with PAI-1, alpha 2-macroglobulin, and C1-inhibitor: studies in patients with defibrination and a fibrinolytic state after electroshock or complicated labor.

Release of tissue plasminogen activator (t-PA) and its interaction with plasma protease inhibitors were studied in two patients with massive defibrination, one after electroshock and soft tissue injury and the other after complicated labor; both had very severe hemorrhage. Large quantities of free t-PA were present in the circulation for several hours. Complexes of t-PA with plasminogen activator inhibitor 1 (PAI-1), alpha 2-macroglobulin and C1-inhibitor were also observed. PAI-1 antigen rose dramatically in both patients, and complexes of t-PA with PAI-1 rose rapidly during the period of observation. In contrast, the complexes of t-PA with alpha 2-macroglobulin and C1-inhibitor, present initially, persisted for short periods only and disappeared when free t-PA disappeared from the circulation. Plasmin was generated initially, as indicated by the presence of plasmin-alpha 2-antiplasmin complexes. Plasma concentrations of alpha 2-macroglobulin, C1-inhibitor, antithrombin III, and alpha 2-antiplasmin were severely depleted initially, but rapidly returned to normal. The observations demonstrate that there is a major release of t-PA in such defibrinating patients, that there is a role for protease inhibitors other than PAI-1 in the regulation of endogenous t-PA, and indicate the great rapidity with which such free t-PA is complexed and cleared.

The bleeding disorder in acute promyelocytic leukaemia: fibrinolysis due to u-PA rather than defibrination.

Three consecutive patients with acute promyelocytic leukaemia who presented with severe haemorrhagic syndromes were studied and the findings contrasted with those of two patients with classical defibrination after electroshock or complicated labour. The leukaemic patients showed no depletion of fibrinogen. There was no evidence of disordered thrombin generation by either intrinsic or extrinsic pathway sufficient to account for their haemorrhage. All, however, showed strikingly enhanced fibrinolytic activity, which could have accounted for bleeding. This fibrinolytic disorder was characterized by free u-PA in the plasma and differed from that seen after classical defibrination, where free t-PA was observed. U-PA was found also in malignant promyelocytes, which may be the source of u-PA activity in the patients' plasma. Bleeding in promyelocytic leukaemia may be primarily a fibrinolytic disorder.

Plasminogen activator inhibitor (PAI-1) in plasma and platelets.

The distribution of PAI-1 in the plasma and platelets of normal individuals and of patients with platelet abnormalities was studied. An ELISA, capable of measuring PAI-1 in plasma at 1.5 ng/ml, and a functional assay of t-PA inhibition were used to assay platelet-free plasma (PFP), platelet-rich plasma in which the platelets were lysed (PRP) and serum. The PAI-1 concentration of normal PFP was 21.0 +/- 7.2 ng/ml (mean +/- SD) and those of PRP and serum were 282.6 +/- 68.0 and 270.3 +/- 71.9 ng/ml. The concentration of PAI-1 in PRP was proportional to the platelet count with 0.67 +/- 0.18 ng/10(6) platelets. Patients with thrombocytopenia had approximately normal PAI-1 concentrations in PFP; the extremely low concentrations in serum or PRP reflected the platelet count. A patient with grey platelet syndrome showed a comparable pattern, confirming that PAI-1 occurs in the platelet alpha-granules and indicating that the plasma concentration of PAI-1 is independent of the platelet pool of PAI-1. The median inhibitory activities towards t-PA were 1.6, 8.7 and 8.3 units/ml in normal PFP, PRP and serum respectively. PAI-1 in PFP had a median specific activity (units/mg PAI-1) about 5-fold higher than platelet PAI-1. Plasma and platelets represent two distinct pools of PAI-1, both of which should be considered in studies on the relationship between circulating PAI-1 and thrombotic disease.

The induction of IFN-gamma production and m-RNAs of interleukin 2 and IFN-gamma by phorbol esters and a calcium ionophore.

Human peripheral blood mononuclear leukocytes were found to produce large amounts of interferon-gamma in response to the calcium ionophore A23187 combined with the phorbol ester mezerein. This effect was synergistic since A23187 and mezerein separately did not induce significant interferon-gamma levels. A23187 plus mezerein induced high levels of interleukin-2 and interferon-gamma mRNAs. The presence of cyclohexamide, which inhibits protein synthesis by greater than 99%, had no effect on the induction by A23187 plus mezerein of mRNA from either gene, indicating that synthesis of proteins such as interleukin-2 is not required for activation of either gene. In addition, using different protocols of stimulation of lymphocytes it was shown that both interleukin-2 and interferon-gamma mRNA steady state levels varied in concert. We conclude that interferon-gamma and interleukin-2 genes are coordinately expressed and activation of transcription of these genes is a primary event of T cell activation independent of production of other proteins.

The regulation of gamma-interferon production by interleukins 1 and 2.

Purified interleukins 1 and 2 (IL-1 and IL-2) were used to investigate their role in the production of gamma-interferon (gamma-IFN). Macrophage depletion from human peripheral blood mononuclear leukocytes (PBML) inhibited gamma-IFN production. Addition of purified IL-1 partially restored IFN production of macrophage-depleted PBML induced by three T cell mitogens (phytohemagglutinin, PHA; concanavalin A, con A; and staphylococcal enterotoxin A, SEA), but had no effect on induction of IFN production by undepleted PBML. Therefore endogenous IL-1 production by macrophages is probably one of the mechanisms by which they act as accessory cells for IFN production by lymphocytes. A monoclonal antibody 9.6 which binds to the sheep erythrocyte (E) receptor found on human T cells inhibited IFN production. Addition of IL-2, but not IL-1, was found to reverse this inhibition. Prostaglandin E2, a macrophage product, inhibited gamma-IFN production induced by PHA, Con A, and OKT3 but usually not SEA. This inhibitory effect was reversible by the addition of IL-2 but not IL-1. In the absence of mitogen IL-1 alone rarely induced any IFN production, although some IFN was produced by PBML from a small minority of donors. Without mitogen IL-2 induced IFN production only at very high concentrations and the added presence of IL-1 did not enhance this induction.

Gamma-interferon production by human low-density lymphocytes induced by T-cell mitogens.

Low-density lymphocytes prepared by Percoll fractionation of human peripheral blood mononuclear leucocytes were found to produce large amounts of interferon-gamma (IFN-gamma) in response to different T-cell mitogens in the absence of macrophages, whilst higher density lymphocytes were strongly dependent on the presence of macrophages for significant IFN-gamma production. The addition of macrophages to the low-density lymphocytes made little difference to their IFN-gamma production. Subsets of the low-density lymphocytes prepared by rosetting with sheep red blood cells produced markedly less IFN-gamma than did the original population; IFN-gamma production could be largely restored by recombining the two low-density fractions. This suggests that IFN-gamma production by low-density lymphocytes whilst macrophage-independent does require co-operation between different cell types. The low-density lymphocytes were enriched for cells bearing the Leu 11 and OKM1 antigens, and for natural killer cell activity. The rosetting fraction was enriched for OKT3 antigen-bearing cells, and the non-rosetting fraction was enriched for Leu 11, OKM1 antigen-bearing cells. Depletion of B cells (surface Ig-positive) by nylon-wool chromatography had no effect on IFN-gamma production by low-density lymphocytes.

Interleukin 2 receptor blockade by anti-Tac antibody inhibits IFN-gamma induction.

Anti-Tac antibody, which binds to the interleukin 2 (IL-2) receptor and thus blocks IL-2 binding to and activation of T lymphocytes, was used to investigate the role of IL-2 in interferon-gamma (IFN-gamma) production. Three T-cell mitogens (phytohemagglutinin, concanavalin A, and the pan-T monoclonal antibody OKT3) were used as IFN-gamma inducers. In each case, anti-Tac antibody clearly inhibited IFN-gamma production. This occurred even under conditions where cellular proliferation (as measured by incorporation of [3H]thymidine) was only slightly inhibited. The inhibitory effects of anti-Tac were reversed by the addition of purified IL-2. Therefore, endogenous production of IL-2 and its binding to the IL-2 receptor are needed for maximum IFN-gamma production.