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Thrombosis of the femoral vein in rats was produced by the injection of thrombin, serum, or sodium morrhuate into ligated venous segments. The histologic effects were followed during resolution or organization of the thrombus and were correlated with the appearance and localization of fibrinolytic activity as assayed histochemically. Lysis of the venous thrombus began immediately when thrombin or serum had been used. Sites of thrombolysis were related to the presence of endothelial cells of venous origin and containing plasminogen activator. Sodium morrhuate destroyed the fibrinolytically active endothelial cells thus delaying thrombolysis. Recanalization was associated with the presence locally of active endothelial cells, originating presumably in the adjacent normal venous endothelium. These results support previous observations on the vascular origin of the plasminogen activator. They elucidate the role played by the fibrinolytically active endothelium in the resolution of venous thrombi. They also confirm and extend previous observations on the role of fibrinolytic activity in tissue repair.

In contrast to the defibrination mediated by the thrombin clotting of fibrinogen, such as in the disseminated intravascular coagulation syndrome, the in vivo induction of defibrination by Ancrod or Reptilase is suprisingly benign and not accompanied by significant changes in most clotting factors or in platelet count. This difference was studied in vitro using an approach based on the structural differences between the thrombin induced fibrin and fibrin formed by Ancrod and Reptilase. The latter two varieties of fibrin were shown to be more susceptible to plasmin proteolysis. In addition, the resulting breakdown products were found to be of smaller molecular sizes than those produced by proteolysis of thrombin induced fibrin. Investigations of biological activities of these fibrinogen derivatives including their anticoagulant effect and its inhibition of platelet aggregation supports this concept.

The fibrinolytic activity of the rat uterus was studied by a histochemical method enabling localization of the activity in the tissues. The activity was caused by a plasminogen activator present in the blood vessels of the uterus. While the fibrinolytic activity in the myometrial vessels changes little, the increase of vascularity at late estrus is accompanied with an increase in fibrinolytic activity of the vessels in the endometrium. After ovariectomy, atrophy of uterus and decrease in endometrial vascularity was associated with loss of fibrinolytic activity. This was reversed by estrogen administration. Progestrone administration following estrogen withdrawal produced a secretory stage with no or only a trace of fibrinolytic activity in the endometrium.

In the eye of man and Rhesus monkey (Macaca mulatta) the vessels of the ciliary body, the iris, and the proximal scleral vascular plexus are fibrinolytically highly active. The trabeculae and the ciliary processes are inactive. The endothelium of the canal of Schlemm of adult man and the junctions of collector channels with the canal of Schlemm in monkey are highly active. In the human fetus and the newborn infant the canal of Schlemm is inactive. Aqueous humor of monkey has slight fibrinolytic activity, and contains small amounts of plasminogen. The findings suggest that fibrinolysis could assist in preventing obstruction by fibrin of the aqueous outflow pathways and could participate in the regulation of outflow of aqueous humor.

Use of the milliwatt CO 2 laser to perform microvascular anastomoses is associated with characteristic histologic changes, including intimal hyperplasia and medial necrosis. The extent of myointimal proliferation after both suture and laser-assisted vascular anastomosis was assessed in the rat femoral artery model. At 2 weeks the average intimal height of the laser-anastomosed vessels was 11.7 ± 2.2 μm (mean ± standard error of the mean) vs. 21.3 ± 3.2 μm for sutured arteries (p

An abnormal substance in the plasma of certain diabetic patients enhances platelet aggregation. There is a correlation between the severity of diabetic retinopathy and the degree of platelet-aggregationenhancing activity in the plasma of adult diabetics. We postulate that increased platelet aggregation leads to the development of ischemic retinal lesions and thereby plays a significant role in the genesis of diabetic retinopathy. Aspirin blocks the action of the aggregation-enhancing activity of diabetic plasma nonspecifically, although it has no effect on the plasma level of the factor. Therefore, therapy with aspirin may be of value in the prevention of diabetic retinopathy.

SummaryA 55-year-old previously well woman noted easy bruising and developed a swollen, painful leg after minimal trauma. A compartment syndrome was diagnosed, and medial and lateral fasciotomies were performed with evacuation of a massive hematoma. However, blood rapidly reaccumulated in the wound. The VILI : C level was 2%, and 4 Bethesda units of factor VIII inhibitor were detected. After initial treatment with clotting factor concentrates and corticosteroids failed to control bleeding or reduce inhibitor titers, gamma globulin, 25 g daily for 5 days, was administered. The inhibitor became undetectable, VIII :C levels rose, and bleeding stopped. However, 5 days later VIII :C levels were again low and bleeding recurred. A second course of gamma globulin, 50 g daily for 2 days, was accompanied by a prompt increase in VIII :C, and uneventful recovery. In conclusion, in this patient with an autoantibody to Vili : C, a response to gamma globulin was observed on two occasions, and the second response came when steroids were being tapered and the patient was on no other medication.

Septic pelvic thrombophlebitis is an uncommon but potentially life-threatening complication of puerperal endometritis. The lack of specific physical findings necessitates a diagnosis based by exclusion on the patient's response to anticoagulation. Fibrinopeptide A (FPA) is the first peptide cleaved from fibrinogen during thrombin-mediated fibrin generation. Because of its short half-life, FPA accurately reflects the level of ongoing fibrin generation. In a preliminary study of 40 puerperal patients, FPA successfully differentiated puerperal fever secondary to endometritis or abscess from fever responsive to a heparin trial. The mean FPA level in patients presumed to have septic pelvic thrombophlebitis was 23.8 ng/ml as opposed to 7 ng/ml in patients with endometritis. No patient with septic pelvic thrombophlebitis as diagnosed by her response to a heparin trial had a level of FPA less than 14 ng/ml. There was no overlap of FPA levels between patients with endometritis or abscess and septic pelvic thrombophlebitis. The data suggest further prospective evaluation of FPA for the diagnosis of septic pelvic thrombophlebitis is warranted.

Recent reports have suggested a correlation between congenital protein C deficiency and tissue necrosis complicating oral anticoagulants (warfarin necrosis). The authors studied blood samples of 13 patients, obtained two weeks to more than six months after warfarin necrosis. Protein C antigen levels were assayed by an enzyme-linked immunosorbent assay method (Diagnostica Stago, France). Factors II, VII, IX, and X were assayed by functional methods, and IX and X additionally by immunologic methods. The results show that 11 of 13 patients with a history of tissue necrosis had low protein C levels, ranging from 23 to 69%, with the normal range being 70-140%. These results confirm that low protein C antigen levels are implicated in the pathogenesis of warfarin necrosis.

The milliwatt CO2 laser was used to anastomose rat carotid arteries in an end-to-side fashion, and this technique was compared to the standard suture technique. Vessels were studied at two to six weeks. All anastomosis were patient and overall, there was a 78.6 percent rate of aneurysm formation in the laser cohort, compared with 7.1 percent with suture (p less than 0.001 Fisher exact). Vessels and aneurysm histology were similar to those previously reported for the end-to-end technique.

The bursting strength of suture- and laser-assisted vascular anastomosis (LAVA) was assessed using a standard rat femoral artery model. Vessels were studied from 1 hour to 3 weeks. LAVA arteries consistently demonstrated lower bursting strengths than those of suture controls, with significant differences at 1 day, 3 days (P less than 0.001), and 1 weeks (P less than 0.01). Return of strength occurred in a pattern reminiscent of wound-healing models. Relatively low bursting strengths at 1 and 3 days in the LAVA cohort may explain the high aneurysm rate reported to complicate this procedure.

Thrombocytopenia complicating heparin therapy is always alarming since the bleeding risk is greatly increased. The observations of Bell et al (Ann Int Med. 85:155, 1976) of a 30% incidence of thrombocytopenia in patients receiving bovine lung heparin was not supported by later reports from Powers et al (JAMA 241:2396, 1979) of only 3.4%. However, the latter study involved the use of heparin prepared from porcine gut mucosal. A prospective randomized study of these two respective heparin preparations was carried out at the VA Lakeside Medical Center on 98 patients to whom heparin therapy was given for the treatment of various forms of thromboembolism. All received a heparin dose that prolonged the activated partial thromboplastin time to l1/2-21/2 times the control level for at least 5 days. 86 patients had heparin for 7 or more days. The observation of platelet counts was carried out for 7 days. 10 patients (10.2%) had a fall in their platelet counts to less than 150×l06/dl during therapy with one of the ten having a platelet count of 95×l06/dl on the 4th day of therapy. All but one of the thrombocytopenias were transient, lasting 1-6 days despite continuation of heparin therapy. Of 49 patients who received porcine heparin, 4 (8.2%) had thrombocytopenia while the incidence was 6 out of 49 (12.2%)in those who received bovine heparin. These results suggest that complications of severe thrombocytopenia are uncommon with heparin derived from both sources.

This report describes the experimental design, methods, and baseline characteristics of patients enrolled in a Veterans Administration Cooperative Study on the effect of aspirin (325 mg t.i.d.) and dipyridamole (75 mg t.i.d.) (110 patients), or placebo (121 patients) on major vascular outcome variables in noninsulin-dependent diabetic patients with either a recent amputation for gangrene (n = 207) or active gangrene (n = 24). It also describes the baseline characteristics of the patients. A total of 231 patients of 563 screened (41%) were enrolled at 11 participating V.A. Medical Centers during a 39 month period. The median age at entry was 60 years, the median duration of diabetes was 10 years, and weight was 110% of desirable. All patients were men. Sixty-eight percent were treated with insulin and 32% with diet alone. Only 42% were smokers at entry, 40% had retinopathy, 61% sensory neuropathy, 42% hypertension, and 29% had a history of myocardial infarction, angina, and/or congestive heart failure. Thirteen percent had a history of cerebrovascular disease. Despite randomization, the treatment group had an increased frequency of a history of cerebrovascular disease (p = 0.01), diagnosed as stroke (p = 0.03), a finding suggesting that the treatment group was at a slightly increased risk for vascular disease upon enrollment in the study. Other baseline variables did not differ significantly between the two groups. This study should provide definitive data on the efficacy of these doses of antiplatelet agents in preventing further vascular disease in diabetic men with gangrene or recent amputation for gangrene, using death due to vascular disease and subsequent amputation of the opposite extremity for gangrene as major outcome variables. It should also give useful information on the effect of antiplatelet therapy on vascular outcome variables such as same side amputations, myocardial infarction, stroke, transient ischemic attack, retinopathy, and renal failure. Finally, the study should provide useful data on the natural history and significance of risk factors in this patient population.

An anabolic steroid, Stanazolol, has been shown to increase AT-III concentration in subjects with both congenital and acquired AT-III deficiency (Thromb & Haem. 43:18, 1980; Thromb Diath Haem. 34:106, 1975). It is also claimed to have beneficial effects on idiopathic recurrent superficial thrombophlebitis and cutaneous vasculitis. In an attempt to elicit the pharmacologic action of this steroid on the fibrinolytic system, the plasma plasminogen of 15 subjects with no known thromboembolic disease were studied before and after administration of Stanozolol, 10 mg/ day for periods of 7-21 days. The plasma plasminogen level was found to increase from 15-63% (mean 35.4%) of baseline level within a period of 7 days, and up to 76%. by day 18. No significant changes were noted on the plasma fibrinogen level nor on the activities of alpha2 plasmin inhibitor, free protease, or plasminogen activator. In vivo plasmin generation by both streptokinase and urokinase was also studied in the plasma samples. The generation rate by either activators was found to be significantly increased along with the rise in plasminogen level. The plasmin generation index (plasminogen level x plasmin generation rate) representing potential amount of plasmin that can be generated in the plasma samples was found to be increased even more so, by Stanozolol administration. Since the successful outcome of thrombolytic therapy depends on the bioavailability of plasminogen, the present findings of an enhancement of plasminogen by Stanozolol has obvious clinical implications.

The dynamics of clot formation using either thrombin or arvin to clot purified human fibrinogen F XIII free fibrinogen and human plasma was studied using the thrombelastograph (TEG). Varying concentrations of these components including calcium were observed for their effects on the overall clotting patterns. The action of plasmin or urokinase on these systems was also evaluated. The production of equal area thrombelastographic tracings required over four times the amount of Ancrod compared to thrombin in the absence of calcium. Calcium ions exerted profound effects upon the TEG configuration inhibiting clot formation at certain concentrations in the Ancrod system, while enhancing the rate and size of fibrin formation in the thrombin systems. These changes were heavily influenced by the ionic strength of the buffer system, and appear related to factor XIII activation. No TEG differences were observed when thrombin or Ancrod formed clots were subjected to proteolysis in the absence of calcium. Enhancement of Ancrod but not thrombin clots subjected to proteolysis in the presence of calcium was observed with early Ancrod samples, but this phenomenon was minimal with more purified Ancrod solutions available recently. Doubling of the control area was demonstrated in some cases with the less pure Ancrod and appeared to be related to the dose of urokinase employed. If one assumes that the lytic agents preferentially attack the residual fibrinogen molecule rather than formed fibrin then greater amounts of fibrin monomer could result and produce a larger initial clot than with Ancrod alone. Repeating these experiments with F XIII free fibrinogen produced the same results. Enhancement effects disappeared when the proteolytic agent was added after clotting had begun, and increased lytic susceptibility of the impure Ancrod systems sometimes occurred under these circumstances. Ancrod and thrombin formed fibrin clots exhibit different characteristics depending upon the nature of the test system. The potential thrombogenic properties of the earlier contaminated Ancrod samples emphasized the importance of using only the pure preparations for therapy in man.

Platelet function during hemodialysis was studied in 27 patients during 62 dialyses on a Cor-dis-Dow Hollow Fiber Artificial Kidney CDAK-4 with anticoagulation by porcine mucosal heparin. Platelet levels fell from 2.08 + 0.52 × 109/1 (Mean ± S.D.) prior to dialysis to 1.74 ± 0.49 × 109/1 after 1/2 hour of dialysis (PThe findings are compatible with an enhanced reactivity of platelets and the concomitant adherence of aggregable platelets upon the dialyzer fibers, leaving an increased fraction of poorly functioning platelets in the circulation. The enhanced reactivity is apparently induced by heparin, increased levels of ionized calcium, and other factors.

The levels of several tumor associated proteases, including plasminogen activators (PA), are elevated in many malignant tumors compared to their benign tumor counterparts. Extracellular matrix degradation mediated by PA may facilitate tumor cell invasion and metastasis. To assess whether PA content correlates with the aggressive phenotype in prostate cancer, we studied these activators in the PC-3 human prostate cell line and PC-3CALN, an aggressive in vivo derived variant cell line. Enzymatic assays using H-D-val-leu-lys-pNA (S-2251) as substrate and peroxidase-anti-peroxidase immunohistochemical techniques were used. In an in vitro chemoinvasion assay, the PC-3CALN variant cell line demonstrated significantly greater invasive behavior than the unselected, parental PC-3 line. The activity of PA secreted by PC-3CALN cells was 3.5 times greater than that of PC-3 cells (p less than 0.01). PC-3 metastases obtained following intrasplenic injection of PC-3 cells had greater PA activities than the corresponding primary tumors. Immunohistochemical studies of PC-3 tumors demonstrated preferential localization of urokinase-type PA to areas of apparent tumor cell invasion. These data suggest a correlation between PA and the aggressive phenotype in this model of human prostate cancer. PA, in particular u-PA, may play a role in the migration and invasion of prostate cancer cells and provide a marker of the aggressive phenotype.

The milliwatt CO2 laser was used to anastomose the femoral artery in the rat. Aneurysm formation was a significant problem occurring in 18.6% of the 113 vessels studied. The rate was 29.0% in vessels examined one week or more following the procedure. Histologic analysis shows loss of media elas atic elements as probable etiologic factor. A parallel study of the bursting strength of sutured vs. lasered vessels showed a significant depression in the laser group as compared to suture at 1 day through 1 week.

We report on unobserved, sudden, and unexpected deaths that occurred in a randomized multicenter trial. The long-term effects of aspirin plus dipyridamole on major vascular outcome variables were studied in 231 non insulin-dependent diabetic men with either a recent amputation for gangrene or active gangrene. Depending upon the definition of sudden death used, there were 14, 22, or 17 deaths in the drug group versus 6, 6, or 3 deaths in the placebo group (p = 0.04, 0.001, or 0.001, respectively). Total deaths from atherosclerotic vascular disease or deaths from all causes did not differ in the two treatment groups. Since this finding of a secondary end point is found only after multiple analyses of the data, it must be interpreted with caution. However, it is suggested that further studies on effects of antiplatelet agents on sudden deaths should be performed.

A synthetic chromogenic substrate has recently been reported for use in the specific measurement of urokinase. This material (Chromozym UK, marketed by Pentapharm, Ltd., Basle) is a synthetic tripeptide linked through an amide bond to the chromogen para-nitroaniline (PNA). The release of free PNA can be monitored spectrophotometrically by measuring the increase of absorbance of light in the range of 380 to 410 nm. The present communication describes our efforts at enhancing the color yield of the assay as well as changing the absorption maximum to a wavelength which can more readily and accurately be measured on inexpensive laboratory spectrophotometers .Bratton and Marshall have developed a method which can be used for the determination of aromatic amines in biological systems. We have modified this method for use in semimicro applications and have adapted it to the measurement of free PNA in solution. After acidification of an aliquot of the enzyme digest with trichloroacetic acid (TCA), the liberated PNA is diazotized with sodium nitrite. Excess nitrous acid is removed with ammonium sulfamate, and the diazotized PNA is reacted with 1-naphthylethylenediamine reagent. The product has a magenta-red color with an absorption maximum of 545 nm. The substrate is not affected by exposure to TCA, and when fresh reagents are used, a low background is obtained. The color yield during actual enzyme assay is amplified twenty fold. Other coupling agents are also currently under investigation.

Routine blood coagulation tests were performed on 431 consecutive patients enrolled in a study of the role of anticoagulation in cancer treatment (VA Cooperative Study #75). Two hundred sixteen control patients were treated with standard therapy, and 215 patients were treated with standard therapy plus sodium warfarin. At the time of entry into the study, the most common abnormalities were elevated fibrinogen levels, platelet counts, and fibrinopeptide A levels. Serial studies demonstrated a steady increase in platelet count and fibrinogen levels before death. Anticoagulation lowered FPA levels but had no significant effect on fibrinogen levels, platelet counts, or euglobulin clot lysis times. An unexpected finding was a dramatic increase in fibrin split product levels after institution of anticoagulation (means +/- SEM = 42.6 +/- 116.4 vs. 2.9 +/- 7.0 mg/L in control subjects; P less than 0.02). This study supports the presence of subclinical activation of blood coagulation in most patients with cancer. Moreover, the preferential activation of fibrinolysis in anticoagulated patients suggests a role for a vitamin K-dependent factor(s) in the regulation of fibrinolysis in patients with cancer.

A series of 125 adult rats was operated upon to perform end-to-end anastomosis of the femoral artery using either a carbon dioxide laser or conventional suture technique. Vessels were inspected at varying time intervals grossly and microscopically. Overall, the rate of aneurysm formation for the laser group was 18.6% (21/113). Late aneurysm formation (1 week or longer after operation) was seen in 29.8% (20/67) of the laser group. No aneurysms were noted in the suture group either early or late. Histological examination of the laser-joined vessels revealed widespread necrosis and loss of elastic elements in the media. In time, abnormal spindle-shaped cells appeared in this damaged layer. Histologically, the aneurysms were indistinguishable from those reported in human cerebral aneurysm cases. This technique provides an experimental aneurysm model and lends support to the acquired/degenerative theory of human cerebral aneurysm formation.

New technical advances have made feasible the utilization of low-powered laser energy for constructive applications. Experience with laser bonding of blood vessels, peripheral nerves, and dura has been obtained. These studies are summarized, and the future potential of laser bonding of tissues of the central nervous system is discussed.

Fifty-six fresh specimens removed during vascular operations were examined histochemically to determine tissue fibrinolytic activity in the endothelium and adventitia. Prosthetic grafts, saphenous vein grafts, saphenous and varicose veins, and atheromatous femoropopliteal arteries were studied with the following results: (1) Normal vein walls (adventitia) were rich in plasminogen activator with minimal fibrinolytic activity in the endothelium. Fibrotic varicose veins showed reduced lysis activity in the adventitia. (2) There was no fibrinolytic activity in the neointima of all prosthetic materials, except where there was capillary loop formation. (3) Lysis was not present in any of the occluded saphenous vein grafts. (4) Fibrinolytic activity was reduced in atheromatous arteries, except in the area adjacent to fibrin plaques. We conclude that plasminogen activator is of vascular origin; that its activity is dynamic; and that absence of fibrinolytic activity may be an important contributing factor in graft failures.

We correlated repeat determinations of platelet aggregate ratios (PAR) and plasma beta-thromboglobulin (BTG) in the right and left arms of thirty-four subjects in order to measure test reproducibility and to evaluate the effects of venipuncture. The reproducibility of PAR on the same blood samples was relatively low but similar to that obtained when the right arm and left arm values were compared, thus indicating little variation secondary to venipuncture. For BTG, the reproducibility on identical blood samples was quite high, but fell significantly when plasma samples from the two sides were correlated. This finding and increased BTG values when obvious blood collection problems occurred, indicated that plasma BTG levels are quite sensitive to venipuncture technique.

Numerous agents have been administered in an attempt to achieve specific biochemical antiplatelet activity. A model of microsurgical trauma was utilized to create a nonocclusive thrombus, similar to what occurs in the postoperative period. Prostacyclin (PGI2) was given in a high intravenous dose which caused in vitro inhibition of platelet aggregation in rats and rabbits. Although hematological and cardiovascular side effects of PGI2 were tolerated, in vivo platelet thrombus formation persisted and constituted 25-75% of the postoperative thrombus. Even though platelets were inhibited by PGI2, other significant stimuli remained at the site of injury for activation and participation of platelets in the formation of a thrombus.

The effects of dextran was studied by thrombelastography (TEG) because it can graphically depict fibrin, formation and dissolution and plate 1st-fibrin interaction during clothing. Dextran 70 in concentrations of 1-8% ware added to samples of, native whole blood (WB), recalcified whole blood (RWB), platelet-rich plasma (PRP) and platelet-poor plasma (PPP) using buffered saline as control. Dextran produced an 13% reduction in clot Stiffness (MA) with native and celite activated WB. The same native WB shewed a 23? prolongation of clotting (R) and a 24% decrease in the rate of clot formation (α), while the celite activated WB R and α were reduced by 17% and 19% respectively. However, using RWB we found only a 10% reduction in MA as a result of dextran addition, suggesting that citrating and recalcification diminished the dextran effects. With FRF (platelets >560°000 dextran did not show any significant reduction in the measured parameters, uhiU FFP gavs the greatest response with a 36% decrease in MA. Results vere similar if FRF was obtained from subjects who had taken aspirin. This indicates the main action of dextran but to be on the fibrin network rather than on platelets or the plate let-fibrin interaction. though this effect is best seen when platelet concent: rations are low. Clot lysis by urokinase or streptokinase was accelerated in the presence of dextran but was reduced by increased platelet concentrations. These results suggest a direct effect of dextran on fibrin formation and may explain the antithrombotic effect of dextran in thit defective fibrin formation occurs.

The objective of this investigation was to assess the effect of 60% sodium diatrizoate on intimal fibrinolytic activity of saphenous vein as it may play an important role in the development of postvenographic thrombophlebitis. Sixteen saphenous vein specimens were obtained from 14 patients during vascular surgical procedures requiring use of the saphenous vein. Immediately after excision, each vein was divided into three segments for study (Groups I, II, and III). Group I specimens were flushed with normal saline and served as controls. Group II specimens were flushed with 60% sodium diatrizoate. Group III specimens were flushed with 60% sodium diatrizoate followed by normal saline 2 min later. Intimal fibrinolytic activity was quantified in each specimen using the modified histochemical method of Todd. The presence of lysis was noted at 10, 20, 30, and 45 min. In Group 1, 5 of the 16 veins demonstrated no baseline intimal fibrinolytic activity and corresponding specimens were not included in the analysis. When comparing Group II to Group I, there was significant delay in intimal fibrinolytic activity with mean appearance times of 36.8 ± 7.8 and 22.3 ± 9.8 min, respectively (P < 0.0005). Likewise, when comparing Group III to Group I, there was significant delay in intimal fibrinolytic activity with times of 37.3 ± 9.3 and 22.3 ± 9.8 min, respectively (P < 0.005). There was no statistical difference between Groups II and III. The fibrinolytic activity of saphenous vein intima is significantly diminished after exposure to sodium diatrizoate. Saline flush does not significantly alter this effect.

✓ Laser-assisted vascular anastomosis (LAVA) is associated with a significant aneurysm problem when it is applied to small arteries. The etiology of this phenomenon was investigated by creating arteriotomies of different lengths and orientation in the rat carotid artery and sealing them with the milliwatt CO2 laser. It was found that increasing the arteriotomy length from 0.5 to 1.0 mm significantly raised aneurysm occurrence (4/17 vs. 25/28, chi-square: p < 0.001) regardless of orientation. Systemic hypertension (systolic blood pressure ≥ 170 mm Hg) also significantly affected the aneurysm rate among the 0.5-mm arteriotomy group, raising aneurysm occurrence from 23.5% (4/17) to 100% (14/14) (p < 0.001). Assuming that the stay-sutures used for LAVA's act as rigid supports, the rate of aneurysm occurrence must be related to the distance between sutures. This phenomenon has been exploited to create a reliable aneurysm model.

The influence of cardiopulmonary bypass on fibrinolytic activity was assessed by a sensitive clot lysis assay in eight patients undergoing coronary artery bypass operations. Fibrinolytic activity increased immediately after cardiopulmonary bypass was begun and remained elevated throughout the period of extracorporeal circulation. At the conclusion of the operative procedure, fibrinolytic activity returned to the normal range in all patients, and no subject had postoperative bleeding.

Little information exists on the population of cancer patients from which individual patients are selected for admission to a clinical trial. In fact, most reports of clinical trials of cancer chemotherapeutic agents begin by describing samples of treated patients but neglect to collect data and describe the population from which the samples were taken. In a multi-institutional VA Cooperative Study in which two different cancer treatments were compared, an attempt was made to screen all lung, colorectal, prostate, and head and neck patients seen at participating hospitals prior to randomization to a therapeutic regimen. Of a total of 2687 patients screened, 437 (16.3%) were randomized and 2250 (83.7%) were excluded for 2981 reasons. Protocol reasons were the basis for 68.6% of all exclusions, 21.3% were physician refusals, and 10.1% were patient refusals. The number of patients randomized did not correlate well with number of patients screened across participating centers. Patients admitted to the study tended to be younger and in better health than excluded patients. Overestimates of randomization rates projected initially from published information point to the need for improved screening data in the planning of future studies. Factors such as screening methods, physician acceptance of the experimental approach, number of competing protocols within each center, and cooperation among medical center departments and personnel all are important ingredients in any screening effort.

The importance of recognizing disseminated intravascular coagulation as the cause of severe bleeding diathesis in a patient with giant hemangioma is illustrated. A sixteen year old boy with multiple giant cavernous hemangiomas had massive local bleeding after each of the three times surgical excision of the hemangiomas was carried out. Detailed laboratory studies performed on the third occasion provided evidence of disseminated intravascular coagulation as shown by the decreased platelet counts and plasma levels of fibrinogen and factors V and VIII, the prolongation of prothrombin time, partial thromboplastin time, thrombin time, and arvin time, the presence of fibrinogen degradation products, and the increased fibrinolytic activity. Cessation of bleeding accompanied by a return of the laboratory values to within normal limits occurred after correction of the disseminated intravascular coagulation with heparin and acetylsalicylic acid. The use of epsilon aminocaproic acid is contraindicated in this situation.

This study examins the role of leukocytes within a thrombus by demonstrating the morphologic detail of their activities, the chemotactic properties of thrombi and the presence of plasminogen and possible plasminogen activator within eosinophils. A model which produces discrete, reproducible platelet thrombi in arteries and veins of dogs allowed timed studies of their early evolution. In this model, the growth of the thrombus was constantly monitored by a flowmeter and the thrombus could thus be removed at a selected period in its formation. It was then studied histologically for fibrin activity and also ultrastructually. Little fibrinolytic activity was found. In contrast to neutrophils which are concerned particularly with the phagocytosis and disruption of platelet aggregates, we observed that eosinophils participate in the lysis and disruption of the fibrin within these aggregates. The fibrin is rarely phagocytosed but is acted on at the surfaces of the eosinophils, usually in shallow invaginations of the cell membranes. The fibrin shows morphologic changes of lysis. It appears that eosinophils and neutrophils are concerned with the transformation of the early fibrin and platelet thrombus, rather than with the resolution of the formed, mainly fibrin and red cell thrombus.

The most widely used form of heparin for the treatment of thromboembolism has for many years been a preparation derived from porcine intestinal mucosa (hereafter referred to as gut heparin). Recently, a preparation of heparin extracted from bovine lung (hereafter referred to as lung heparin) was made available commercially for therapeutic purposes. Novak et al. (2), in 1972, reported that blood samples obtained after intravenous administration of gut heparin to human volunteers showed a tendency toward shorter platelet aggregation time and longer aggregate dispersion time in response to ADP, whereas volunteers given lung heparin exhibited changes in the opposition direction. They also demonstrated that platelet thrombus formation in vitro using Chandler’s loop technique was accelerated in the blood samples obtained after injection of gut heparin, compared with that after injection of lung heparin. Goldberg et al. (1) reported that the incidence of loss of radial arterial pulse that followed brachial arterial catheterization with gut heparin as an anticoagulant was significantly reduced when lung heparin was used.

A report of anti-Pr cold hemagglutination associated with livedo reticularis is presented. Livedo reticularis is descriptive of the superficial venous system appearing when blood flow is altered in this area. Cold antibody directed against the Pr antigen of the red cell membrane can cause hemagglutination, thereby altering blood flow in cooler areas of the body. This patient had livedo reticularis approximately 8 months prior to detection of the anti-Pr cold agglutinin.

A method is described for amplifying the color of 4-nitroaniline which is produced during enzyme catalyzed amidolysis of synthetic chromogenic substrates. The liberated chromogen is directly coupled with p-dimethylaminocinnamaldehyde to yield a colored schiffbase compound. The color complex has an absorption maximum at 570 nm and, under the reaction conditions described, has a molar absorbancy of 9.1 × 10 4 . The application of this method is presented for the enzyme urokinase using two different chromogenic substrates. A micromethod adaptation of this method is also described. This method can be used to amplify the color obtained in all enzyme assays where 4-nitroaniline is the liberated chromogen.

SUMMARY Clinical and pathological observations are presented on five patients with scleroderma who developed Thrombosis of a major vessel. Three died following intestinal infarction or limb gangrene and two had digit or extremity amputations. Severe intimal thickening of major arteries with thrombus formation was noted but no significant abnormality was found in the clotting activity of the blood. Histochemical studies in three cases suggested a reduction of fibrinolytic activity at the site of thrombosis in the diseased vessels. These studies support the view that the vascular system is profoundly altered in scleroderma and may play an important role in some manifestations of the disease.

✓ The laser-sealed arteriotomy (LSA) technique was used to create experimental aneurysms in the rat carotid artery. Animals were reexplored 2, 4, and 8 weeks following LSA, at which time the aneurysms were measured and subjected to a bursting strength pressure. In addition, a group of hypertensive rats with LSA was also tested 2 weeks after surgery. The LSA procedure produced aneurysms of a stable size and bursting pressure over the time studied. The bursting pressure technique may be applicable for assessing aneurysm therapy in an experimental setting.

NVESTIGATIONS during the past 3 decades have firmly established that the fibrinolytic system is an integral part of the hemostatic mechanism and that its derangement may contribute to the pathogenesis of thrombosis’” (this has been extensively reviewed in this symposium and elsewhere). The recent availability of two plasminogen activators, urokinase (UK) and streptokinase (SK), as promising therapeutic agents has not only stimulated much interest among workers in the field of thrombosis, but has also attracted the attention of investigators in other disciplines. This symposium has focused on a multidisciplinary review of the recent advances on the subject of fibrinolysis ranging from knowledge gained at the molecular level to the results of recent therapeutic trials. At this juncture, one might ponder over the various problem areas requiring the most attention and what may be in store for us in the future. This article, the last in the series, is an attempt to provide the reader with a broader perspective. The ultimate goal of any study must include an increased understanding of the pathogenesis of occlusive vascular disease with their accompanying complications, as well as obtaining better therapeutic results. These may be accomplished through more work done in the following areas.

Platelets were studied for the presence of antithrombin (thrombin amidolytic inhibitory) activity. Platelet rich plasma contained more antithrombin activity than platelet poor plasma. This activity could be washed from a platelet pellet. Antithrombin activity increased on sonication of platelets but not following aggregation. Platelets contain antithrombin activity connected with the membrane and not involved with the release reaction.

In patients with pulmonary emboli, resolution has been shown to be more rapid in those receiving urinary urokinase than in those receiving heparin alone. A different source of urokinase has now been developed, namely human kidney cells grown in tissue culture. In a randomized, multicenter trial, two groups of 15 patients with pulmonary embolism received either the urinary or tissue culture urokinase. Blood samples prior to, during and after treatment were compared with regard to biochemical changes in the plasma fibrinolytic system. Both agents caused strikingly similar rates, degrees and durations of response, as reflected in the whole blood euglobulin lysis time, unheated fibrin plate lysis zones, 125-I tagged clot lysis, plasma plasminogen, plasma clottable protein and serum fibrin/fibrinogen degradation products. Bleeding occurred in about 50% of both groups of patients, primarily from cutdown sites. The results clearly indicate that the pharmacologic effect of tissue culture urokinase was the same as that of urinary urokinase, and it is reasonable to expect that both materials will be equally effective in the hemodynamic and clinical aspects of patients with pulmonary embolism.

The hypothesis that atheromatous plaques originate as intimai collections of blood components was first advanced by Rokitansky (1). This hypothesis has since been revived by Duguid (2) and others (3, 4). Recent findings in support of this concept include the demonstration that the intimai deposits may consist of platelets as well as fibrin. The presence of high thromboplastic activity in the intimai layer of blood vessels, especially arteries (5), provides a mechanism for fibrin or platelet deposition. Additionally, any increase in the coagulability of the circulating blood would facilitate the process. On the other hand, fibrinolytic activity is high in the vascular intima, though less active in arteries than in veins, and could be important in the removal of mural thrombi.