Anthony P. Fletcher

Biologic effects of transdermal estradiol.

Abstract We conducted a dose–response study in 23 postmenopausal women to compare the physiologic effects of transdermal estradiol and oral conjugated equine estrogens. The doses studied were 25, 50, 100, and 200 μg of transdermal estradiol per 24 hours, and 0.625 and 1.25 μg of oral conjugated estrogens. Transdermal estradiol increased circulating concentrations of estradiol and estrone. Oral conjugated estrogens also raised the levels of estrogen, particularly estrone. Both preparations lowered gonadotropin levels, decreased the percentages of vaginal parabasal cells, increased the percentage of superficial cells, and lowered urinary calcium excretion. The effects of 0.625 and 1.25 mg of oral estrogens were similar to those of 50 and 100 μg of transdermal estradiol per 24 hours, respectively. Oral estrogens significantly increased circulating levels of renin substrate, sex-hormone–binding globulin, thyroxine-binding globulin, and cortisol-binding globulin; transdermal estradiol had no effect. The higher...

THE MAINTENANCE OF A SUSTAINED THROMBOLYTIC STATE IN MAN. I. INDUCTION AND EFFECTS

coccal metabolism, is a highly effective activator of human plasminogen. Plasmin, the enzyme formed following plasminogen activation, exerts powerful proteolytic and fibrinolytic effects at neutral hydrogen ion concentrations, which in vivo mediate the mechanisms of physiological fibrinolysis. Consequently, hopes have been entertained that the intravenous injection of streptokinase, or of streptokinase-activated plasmin, might prove to be of benefit in the therapy of human thromboembolic disease. Animal experiment, despite the lessened effectiveness of streptokinase as an activator of animal plasminogen and the difficulties of species variability, has yielded striking findings. The intravenous injection of very large doses of streptokinase has been shown to produce lysis of artificially produced thrombi in the arteries of dogs (1) and in the veins of rabbits (2), to cause the clearance of peritoneal exudate evoked by trauma (3) and more recently to prevent or remove fibrinoid lesions secondary to the generalized Shwartzman response (4). These findings appear to be of unequivocal significance but the precise mechanism of their production has been uncertain.

Thrombolytic Therapy in Thrombosis: A National Institutes of Health Consensus Development Conference

Excerpt For over three decades, the primary method of therapy used by almost all physicians for the management of acute deep-vein thrombosis and pulmonary embolism has been anticoagulation. This fo...

STUDIES ON THE THROMBOLYTIC ACTIVITY OF HUMAN PLASMA

The process of in vivo clot dissolution, termed thrombolysis,l is complex, involving the interaction of clot components with the surrounding plasma. Participating in this interaction are plasminogen, plasminogen activator, plasmin, the plasmin in-hibitory activity of plasma, and fibrin (1). Although much is known of the nature and quantities of individual components, the complexity of the thrombolytic process has led to difficulty in assessment of the overall capability of the plasma for effecting clot lysis under physiological conditions-an activity hereafter termed plasma thrombolytic activity. Plasma thrombolytic activity is a property of major physiological significance (2, 3) but hitherto the technical methods used for its assay have been imperfect. Assays involving determination of whole blood or plasma clot lysis time are valuable for detecting markedly enhanced thrombo-lysis but are inadequate for measurement of low levels of thrombolytic activity due to the very long lysis times found and the lack of a precise end-point. Other assays have involved physicochemi-cal alterations of the plasma such as dilution (4, 5), isolation of the euglobulin fraction (6, 7) and extraction with organic solvents (8). Such physi-cochemical procedures isolate or affect to a variable degree one or more components of the thrombo-lytic process and, although valuable for specialized purposes, disturb the complex balance between the individual plasma components (1). Consequently, assays of this nature are unsuitable for other than qualitative determination of plasma thrombolytic activity. 1 The term thrombolysis is used to designate a process by which preformed clots are lysed, and its use does not imply specific reference to pathological states (1). In order to circumvent these limitations, a sensitive measure of plasma thrombolytic activity was developed in which unaltered plasma is tested. In principle the method involves the determination of radioactivity released from isotopically-labeled human plasma clots immersed in unaltered plasma. Although an in vitro procedure, the use of unaltered plasma and preformed clots mimics in vivo conditions and permits the obtaining of physiologically relevant measurements. Using this isotopic clot assay, measurements of plasma throm-bolytic activity have been made on plasma obtained from healthy adults, from adults following stress, after the administration of drugs, and from individuals with disease. The results indicate that plasma obtained from nonstressed normal adults exhibits thrombolytic activity due primarily to the presence of a plasminogen activator and that this activity varies as a result of stress and disease. MATERIALS AND METHODS I131-trace-labeled bovine fibrinogen 2 was prepared as previously described …

Enzymic lysis of plasma clots: The influence of fibrin stabilization on lysis rates☆

Fibrin clots, freshly formed from recalcified plasma, displayed high susceptibility to lysis by the plasminogen activator, urokinase, or the proteolytic enzymes, plasmin or trypsin; later these clots became insoluble in 5 m urea or 1% monochloroacetic acid and developed increased resistance to enzymic lysis (5- to 10-fold that of the unstabilized clot). In contrast, clots formed from EDTA plasma and clotted with thrombin usually remained soluble in solvents capable of rupturing hydrogen bonds, and did not develop resistance to enzymic lysis. Transamidation inhibitors (glycine amide, methylester, and glycyl derivative) and sulfhydryl inhibitors (iodoacetamide, p-chloromercuribenzoic acid, etc.) inhibited fibrin stabilization and the development of clot resistance to enzymic lysis. Only limited correlation existed between conventional solubility measures of clot stabilization and clot resistance to enzymic lysis, the latter increasing after solubility criteria demonstrated fibrin stabilization. It is suggested that clot resistance to enzymic lysis may constitute an additional valuable measure and criterion of fibrin stabilization.

The influence of pregnancy upon blood coagulation and plasma fibrinolytic enzyme function

Abstract Fibrinogen catabolism has been studied in 27 patients from early pregnancy through delivery and up to 4 months post partum using the noninvasive technique of plasma fibrinogen chromatography. This technique quantifies in plasma the percentage and concentration of high-molecular weight fibrinogen or fibrinogen/fibrin complexes (HMWFC), which reflect the rate of fibrin formation in vivo, native fibrinogen, and derivatives of fibrinogen smaller than the native molecule resulting from the actions of the enzyme plasmin on fibrinogen, an assay reflecting the rate of fibrinogenolysis. Plasma fibrinogen chromatographic findings were similar to control findings during the first gestational month but during the second gestational month plasma HMWFC percentage and concentration were elevated twofold to threefold over control values and thereafter increased with gestational age, being fivefold control values prior to delivery. Plasma fibrinogen increased by the third month and its increase was significantly (p

Association between oral contraceptive use and thromboembolism: A new approach to its investigation based on plasma fibrinogen chromatography

Longitudunal and cross-dectional blood coagulation studies were made in patients receiving oral contraceptive therapy and in unmedicated women used as control subjects. These studies have included use of a new procedure, plasma fibrinogen chromatgraphy, which, by assay for a high molecular weight fibrinogen complexes in plasma, detects or excludes the presence of small thrombi, even when these are of the clinically silent type. New contraceptives users (n=154) received either Ovulen (100 pg of mestranol) or Demulen (50pg of ethinyl estradiol) and were followed serially for one year. During the cross-sectional study (193 women and 1,350 samples), serial examination was preformed on those taking oral contraceptives for 3 months to 10 years. Over-all, pathologic plasma fibrinogen chromatographic findings, indicative of thrombosis, were detected in 6 per cent of hte control examinations and in 27 per cent samples from oral contraceptive users. These findings suggest that oral contraceptive users developed mainlyclinically silent thrombotic lesions, with four-to-fivefold greater frequency than the control subjects. Consequently, it is inferred that they are at four-to fivefold greaterrisk of developing clinically overt disease, a risk factor estimate in line with that derived by epidemiologic study.

Effect of urokinase antiserum on plasminogen activators: demonstration of immunologic dissimilarity between plasma plasminogen activator and urokinase

Antiserum against purified human urokinase was produced by immunization of Hartley strain guinea pigs. The antiserum was capable of neutralizing the plasminogen activator activity of the antigen and of native urokinase in human urine. The antiserum did not inhibit plasminogen activators of bacterial origin, i.e., streptokinase and staphylokinase; neither did it inhibit urokinase from nonprimate mammals, i.e., dog, pig, rabbit, guinea pig, nor tissue activator or tissue culture supernatants from porcine sources. Partial cross-reactivity against urokinase from primates, i.e., rhesus monkey and baboon, was noted as well as with supernatant from rhesus kidney tissue culture. In vitro studies showed lack of immunologic identity between human urokinase and human milk activator or human tissue activator from adrenal sources but demonstrated immunologic identity between human urokinase and the supernatant from human kidney tissue culture. In vivo studies in man failed to show detectable levels of urokinase activity in peripheral venous or renal venous blood under a variety of clinical states and when stimuli such as exercise, electroshock therapy, or nicotinic acid were used to enhance plasminogen activator activity in the plasma. The results establish that human plasma activator, milk activator, and tissue activator from the adrenals are immunologically distinct from human urokinase.

DEVELOPMENTS IN FIBRINOLYTIC THERAPY FOR THROMBO-EMBOLIC DISEASE

Excerpt Intravascular thrombi in animals may be dissolved by activating the naturally occurring fibrinolytic enzyme system.1, 2In figure 1 (on the left), there is illustrated an experimental thromb...

Severe glomerulonephritis complicated by coagulopathy: Treatment with anticoagulant and immunosuppressive drugs

Serial determinations, using plasma fibrinogen gel chromatography as well as standard methodology, demonstrated that six children with severe glomerulonephritis, characterized on renal biopsy by glomerular necrosis and crescent formation, had persistent evidence of intravascular coagulation. Based on these observations, therapy with anticoagulants and azathicoagulants and azathioprine was instituted for one year; treatment with anticoagulants was continued for a second year. Anticoagulant therapy was initiated with heparin, followed by oral anticoagulation with phenindione and dipyridamole. In contrast to our earlier experience with similar patients, each of the present patients improved. Urinalyses returned to normal and glomerular filtration rates to near normal values in all patients at the end of the treatment period and have remained so for up to 3.9 years since treatment has been completed. Post-treatment biopsies showed remarkable improvement, with virtually no glomerulosclerosis even in patients who had had a high incidence of glomerular crescents before treatment. It is suggested that the therapeutic regimen favorably influenced the natural history of disease and that plasma fibrinogen chromatographic findings may be helpful in selecting patients likely to benefit from the use of anticoagulant therapy.