Eastern Canadian Colorectal Cancer Consensus Conference 2017

The annual Eastern Canadian Gastrointestinal Cancer Consensus Conference 2017 was held in St. John's, Newfoundland and Labrador, 28-30 September. Experts in radiation oncology, medical oncology, surgical oncology, and cancer genetics who are involved in the management of patients with gastrointestinal malignancies participated in presentations and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses multiple topics in the management of gastric, rectal, and colon cancer, including ■ identification and management of hereditary gastric and colorectal cancer (crc);■ palliative systemic therapy for metastatic gastric cancer;■ optimum duration of preoperative radiation in rectal cancer-that is, short- compared with long-course radiation;■ management options for peritoneal carcinomatosis in crc;■ implications of tumour location for treatment and prognosis in crc; and■ new molecular markers in crc.

Acyl-Enzymes as Thrombolytic Agents in Dog Models of Venous Thrombosis and Pulmonary Embolism

A quantitative model of venous thrombosis in the beagle dog is described. The model was adapted to permit ageing of isolated experimental clots in vivo. A model of acute pulmonary embolism in this species is also described. In the venous thrombosis model, infusion of streptokinase (SK) or SK-activated human plasmin gave significant lysis but bolus doses of SK. plasmin complex were ineffective. Active site anisoylated derivatives of SK. plasminogen complex, SK-activated plasmin and activator-free plasmin were all active when given as bolus doses in both models. At lytic doses, the acyl-enzymes caused fewer side-effects attributable to plasminaemia than the corresponding unmodified enzymes.

Acylated Derivatives of Streptokinase-Plasminogen Activator Complex as Thrombolytic Agents in a Dog Model of Aged Venous Thrombosis

A procedure is decribed for the establishment of experimental clots, aged in vivo for 72 hr, in the jugular vein of beagle dogs. Two acylated derivatives of streptokinase-human (lys) plasminogen activator complex with greatly differing deacylation rates under physiological conditions were compared as thrombolytic agents in the model. These were BRL 26921 (deacylation halflife, 40 min) and BRL 33575 (deacylation half-life c. 17hr). The pharmacokinetic clearance rate of BRL 33575 from the circulation was studied and gave a clearance half-life of about 7 hr. BRL 33575 was found to be the superior agent in lysing 72 hr aged clots, being effective at a single bolus dose of 420 μg/kg or in three equal divided doses of 140 μg/kg given at 12 hr intervals. The single dose regime gave moderate systemic plasminogen activation, and the effect was significantly reduced with the divided dose regime. Infusion of freshly formed streptokinasehuman plasminogen activator complex at 420 μg/kg over 15 hr gave little thrombolysis despite marked systemic plasminogen activation.

Acyl-Enzymes as Thrombolytic Agents in a Rabbit Model of Venous Thrombosis

A derivative of human lys-plasmin in which the active site has been reversibly acylated (BRL 26920; p-anisoyl human lys-plasmin) has been examined as a fibrinolytic agent in a previously described rabbit model of venous thrombosis and shown to be significantly more active and less fibrinogenolytic than free plasmin. A p-anisoylated derivative of a streptokinase (SK)-activated plasmin preparation was significantly less fibrinogenolytic in vivo than the non-acylated enzyme. Acylation increased the fibrinolytic activity of preparations of SK-plasmin activator complexes. BRL 26921, the active site anisoylated derivative of the primary 2-chain SK-plasminogen complex was the most potent fibrinolytic agent studied. SK-Val442-plasminogen complexes, free or acylated, were biologically inactive in this model and confirm the essential nature of fibrin binding processes for effective thrombolysis in vivo.

The Evaluation of Plasmin and Streptokinase Activator Complexes in a New Rabbit Model of Venous Thrombosis

A new quantitative model for the examination of potential thrombolytic agents is described. A thrombus was formed in the inferior vena cava of the rabbit, using 125I-labelled fibrinogen mixed with a standard amount of thromboplastin. The thrombus was anchored securely by means of a woollen thread inserted longitudinally into the lumen of the vein. Thrombotic extension of the radioactive clot and rethrombosis during the experimental period (5 h) were prevented by the administration of intravenous heparin. In control animals, the thrombus remained stable and there was no rise in the radioactivity of the circulating blood during 5 h. In animals given thrombolytic agents, lysis could be followed continuously by measuring the rise in blood radioactivity. Total lysis was determined by counting the radio-label in the residual clot after treatment.

The model has been used to study the thrombolytic activity of streptokinase-human plasminogen complexes, activator-free plasmins of human and porcine origin, and human plasmin produced by streptokinase (SK) activation of human plasminogen. The role of activator complexes in the thrombolytic activity of SK-activated plasmin is discussed.

The Thrombolytic Activity of Streptokinase in the Rabbit

The activity of streptokinase (SK) has been examinEd in a rabbit model of venous thrombosis. Significant thrombolysis was observed at low doses of SK without evidence of systemic activation of the fibrinolytic system. The origidn of the specificity of SK-induced fibrinolysis in the rabbit was explored, using a chromogenic substrate coupled assay to measure the enhancement of plasmin generation in the presence of rabbit fibrin. The results obtained suggest that rabbit fibrin influences the fibrinolytic system at three points, viz: the assembly of an activator complex from rabbit plasminogen and SK; the activity of that activator complex towards further rabbit plasminogen; and the activity of the resulting rabbit plasmin in the presence of plasma inhibitors.