SummaryWe reported previously that habutobin, a thrombin-like enzyme from Trimeresurus flavoviridis venom, clotted only rabbit fibrinogen, whereas human, monkey, bovine, dog, rat and guinea-pig fibrinogens were unaffected. In the present study, we investigated the cleavage site of the rabbit Aα chain by habutobin. The fibrinopeptide released by habutobin was identical to the fibrinopeptide A released by thrombin, and its amino acid sequence corresponded to Aα 1-16 of rabbit fibrinogen. It was clarified therefore that habutobin cleaves the Arg16-Gly17 bond in the Aa chain of rabbit fibrinogen.
We examined the effect of pH on the extraction of urokinase-type plasminogen activator (u-PA) and plasminogen activator inhibitor-1 (PAI-1) from paranasal sinus mucous membrane associated with chronic sinusitis and antrochoanal polyps. The specific activity of u-PA extracted with buffer at pH 7.4 was stronger than that extracted with buffer at pH 4.2. The antigen level of u-PA extracted with the acidic buffer was significantly higher than that extracted with the neutral buffer. In contrast, the difference in antigen levels of PAI-1 extracted with the acidic buffer and neutral buffer was not significant. Based on these results, we inferred that the u-PA-PAI-1 complex was extracted by the acidic buffer and the activity of u-PA was therefore decreased.
We measured the maximum aggregation rate (MAR) of platelets in 770 patients with malignant head and neck tumors, 55 patients with benign tumors of the head and neck, and 164 healthy people as a control group. The results were as follows: 1. the mean MAR value of patients with malignant tumors was significantly higher than the control group mean value; 2. prior to treatment, the mean MAR value increased with advancing tumor stage; 3. both MAR values of relapsed or metastasized patients and of nonsurvivors in stage III and IV increased significantly compared with survivors or patients recovering from malignant tumors. The results of the present study suggest that MAR values of patients with malignant tumors of the head and neck may serve as indicators in evaluating therapeutic procedures and prognosis.
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