Dynamics of parameters of heart rate variability after radiofrequency ablation in patients with paroxysmal supraventricular tachycardia: holter ECG monitoring data

Changes of parameters of heart rate variability (HRV) in patients with supraventricular tachycardia (SVT) immediately after radiofrequency ablation (RFA) have been demonstrated earlier. However dynamics of HRV parameters after RFA has not been sufficiently studied. For elucidation of dynamics of HRV parameters in patients with SVT after RFA we conducted analysis of HRV basing on data of 24 hour Holter ECG monitoring before RFA, on day 2, in 1 week and 1 month after intervention in 27 patients with paroxysmal SVT. Statistically significant lowering of temporal (SDNNi, RMSSD, NN50, pNN50) and spectral (VLF, LF, HF) HRV parameters were found on day 2 and in 1 week after RFA compared with data obtained before intervention. In 1 month after RFA the studied parameters of HRV did not differ from baseline values. Reversible changes of HRV parameters evidencing for transitory autonomic dysfunction are observed after RFA.     

Echicetin: a snake venom protein that inhibits binding of von Willebrand factor and alboaggregins to platelet glycoprotein Ib

Echicetin, a new protein isolated from Echis carinatus venom by reverse phase and ion exchange chromatography specifically inhibited agglutination of fixed platelets induced by several platelet glycoprotein Ib (GPIb) agonists, such as bovine von Willebrand factor (vWF), alboaggregins, and human vWF in the presence of botrocetin. Unlike alboaggregins, echicetin bound to GPIb but did not induce agglutination of washed or fixed platelets. In contrast to disintegrins, it did not block adenosine 5'-diphosphate (ADP)-induced platelet aggregation in the presence of fibrinogen. The apparent molecular weight of echicetin measured on sodium dodecyl sulfate (SDS) gel electrophoresis was 26 Kd under nonreducing conditions. On reduction, echicetin showed 16 and 14-Kd subunits suggesting that the molecule is a dimer. Reduced echicetin retained its binding activity and its inhibitory effect on the agglutination of fixed platelets induced by bovine vWF. 125I-echicetin bound to fixed platelets with high affinity (kd = 30 +/- 1.8 nmol/L) at 45,000 +/- 2,400 binding sites per platelet. The binding was selectively inhibited by a monoclonal antibody to the 45-Kd N-terminal domain of platelet GPIb, but not by monoclonal antibodies to other regions on GPIb. Binding of 125I-bovine vWF to fixed platelets was strongly inhibited by echicetin. In contrast, bovine vWF showed a much weaker inhibitory activity on binding of 125I-echicetin to platelets. The half life of echicetin in blood was approximately 170 minutes with no detectable degradation. Echicetin significantly prolonged the bleeding time of mice, suggesting that it may inhibit vWF binding to GPIb in vivo as well as in vitro.     

Effect of surfaces on fluid-phase prekallikrein activation

The activation of prekallikrein by factor XII fragments (XIIf), during incubation in plastic tubes was previously noted to be increased by high molecular weight (HMW) kininogen as well as other plasma proteins. In this report, we investigated the mechanism responsible for this increase. Although we confirmed that HMW kininogen, bovine serum albumin, fibrinogen, cold insoluble globulin, and mixed phospholipids apparently increased prekallikrein activation, we found that the product of prekallikrein activation (kallikrein) lost substantial activity in less than 0.5 min after exposure to a variety of fresh surfaces. This loss was partially prevented by the presence of various proteins and phospholipids. Similar protection against inactivation of XIIf, the enzyme in this reaction, was also found. In contrast, no loss of the substrate, prekallikrein, was observed during incubation. The loss of kallikrein activity was found to be proportional to the surface area of the incubation vessel as well as the concentration of kallikrein. Further loss of kallikrein activity could also be prevented by pretreating the vessel with kallikrein. We therefore conclude that various substances apparently affect prekallikrein activation in a purified system by preventing the enzyme and product in the reaction mixture from losing activity due to adsorption to a surface.     

Fractionated total-body irradiation and high-dose etoposide as a preparatory regimen for bone marrow transplantation for 94 patients with chronic myelogenous leukemia in chronic phase

Ninety-four consecutive patients with chronic myelogenous leukemia in first clinical chronic phase, median age of 34.0 years (range, 6.8 to 52.4 years), with a histocompatible sibling donor, were treated with fractionated total body irradiation (1,320 cGy) and high-dose etoposide (60 mg/kg) followed by allogeneic bone marrow transplantation (BMT). The median time from diagnosis to BMT was 7.0 months (range, 2.3 to 72.0 months). Sixty patients were treated before BMT with hydroxyurea alone, four patients with busulfan alone, one patient with interferon alone, and the other 29 patients were treated with various combinations of these drugs. Cumulative probabilities of overall survival, event- free survival, and relapse at 5 years were 73%, 64%, and 14%, respectively. The median follow-up time for surviving patients was 38 months, ranging from 12 to 88 months. By stepwise Cox regression analysis, significant prognostic variables were age at transplant, acute graft-versus-host disease > or = grade II, cytomegalovirus- associated interstitial pneumonitis, and years from diagnosis to BMT.     

分枝桿菌(Mycobacterium sp.M12)降解甾醇侧链的研究

分枝杆菌(Mycobacterium sp.M12)能将胆固醇,3β-乙酰氧基胆固醇,谷甾醇以及3β-乙酰氧基谷甾醇降解成△³-雄甾烯-3,17-二酮(4AD)及少量的△^1.4-雄甾烯-3,17-二酮(ADD)。4AD的收率分别为69%,70%,26%,22%。对该菌株降解胆固醇侧链的最适条件进行了研究。