In praise of H2O2, the versatile ROS,and its vanadium complexes

Hydrogen peroxide (H₂O₂) is generated in mitochondria in aerobic cells as a minor product of electron transport, is inhibited selectively by phenolic acids (in animals) or salicylhydroxamate (in plants) and is regulated by hormones and environmental conditions. Failure to detect this activity is due to presence of H₂O₂-consuming reactions or inhibitors present in the reaction mixture. H₂O₂ has a role in metabolic regulation and signal transduction reactions. A number of enzymes and cellular activities are modified, mostly by oxidizing the protein-thiol groups, on adding H₂O₂ in mM concentrations. On complexing with vanadate, also occurring in traces, H₂O₂ forms diperoxovanadate (DPV), stable at physiological pH and resistant to degradation by catalase. DPV was found to substitute for H₂O₂ at concentrations orders of magnitude lower, and in presence of catalase, as a substrate for user reaction, horseradish peroxidase (HRP), and in inactivating glyceraldehyde-3-phosphate dehydrogenase. superoxide dismutase (SOD) -sensitive oxidation of NADH was found to operate as peroxovanadate cycle using traces of DPV and decameric vanadate (V₁₀) and reduces O₂ to peroxide (DPV in presence of free vanadate). This offers a model for respiratory burst. Diperoxovanadate reproduces several actions of H₂O₂ at low concentrations: enhances protein tyrosine phosphorylation, activates phospholipase D, produces smooth muscle contraction, and accelerates stress induced premature senescence (SIPS) and rounding in fibroblasts. Peroxovanadates can be useful tools in the studies on H₂O₂ in cellular activities and regulation.     

Standardisation of thrombin generation test - which reference plasma for TGT?: An international multicentre study

We have previously shown that standardisation and normalization of results improve the intercentre variability of the calibrated automated thrombin generation test (TGT). We suspected that the source of reference plasma (RP) might be a contributing factor to variability and compared 5 commercial RP and a RP provided by the NIBSC, in an international, multicentre study. The detailed composition of the 6 tested plasma samples was determined in the Haemostasis Labotatory in Lyon. The lot to lot consistency, intra-assay, inter-assay variability were calculated for all tested plasmas. The RP and 3 plasma samples (a normal control, a hypocoagulable and a hypercoagulable plasmas) were tested over 6 days, in 5 European centres. Results were normalised against each of the tested RP and intercentre variability of results was compared. All laboratories used the same reagents. Before normalization, the inter-centre variability was 19.8 to 27.3%. After normalization, we observed a significantly improved inter-laboratory variation with all tested RP, despite differences between them. These results clearly demonstrate that the inter-centre variability of TGT can be significantly reduced by using a reference plasma normalization, and that certain RP have a better capacity to reduce this variability than others.     

流动注射氢化物发生原子吸收光谱法测定人发中痕量汞

目的：建立测定人发中痕量汞的新方法：方法：用自制的电热恒石英管为吸收池，用流动注射氢化物发生原子吸收光谱法联合技术进行测定，结果：选用了最佳工作条件，提高了方法的精密度，准确度，检出限为0.1ng/g,线性范围0.000-2.520ug/g,r=0.9996，回收率为92％－98％，相对标准偏差为1．4％－3．4％，结论：该方法精密度高，准确度好，适用于人发中痕量汞的测定。     

Washing Machine Associated 50 Hz Detected As Ventricular Fibrillation by An Implanted Cardioverter Defibrillator

SABATÉ, X., et al. : Washing Machine Associated 50 Hz Detected As Ventricular Fibrillation by An Implanted Cardioverter Defibrillator. This case report describes a patient with an automatic ICD who suffered a defibrillation shock without warning symptoms. An electrical interference can be observed in the stored EGM of the episode. The patient explained that the moment he felt the shock he was touching a washing machine. After correct grounding of this machine the patient did not suffer more inappropriate shocks.     

Functional Regeneration of a Severed Peripheral Nerve With a 7‐mm Gap in Rats Through the Use of An Implantable Electrical Stimulator and a Conduit Electrode With Collagen Coating

Objective: This paper examined the efficacy of an implantable electrical stimulator in rats for the functional regeneration of peripheral nerves. Materials and Methods: The implantable electrical stimulator was fabricated on a polyimide‐based conduit with an integrated electrode, a stimulation chip, and a battery; 3 mg/mL of collagen gel was coated onto the conduit surface and electrical stimulation (20 µA, 100 µs, and 100 Hz biphasic current) was continuously applied between the nerve stumps for four weeks. The stimulator was tested on a severed sciatic nerve with a 7‐mm gap in rats. The effects of both the electrical stimulation and the collagen application were examined. Results: Functionality was evaluated through walk track assessments and by recording the action potential of the regenerated nerve. Immunohistochemical staining of the regenerated nerve was done using peripheral myelin protein 22. Conclusion: The results suggest that the functional recovery of a severed peripheral nerve by the proposed implantable electrical stimulator was achieved through electrical current stimulation along the use of a collagen coating on the conduit surface.     

Thrombin generation in patients with factor XI deficiency and clinical bleeding risk

Summary. Factor XI (FXI) deficiency is a rare bleeding disorder. Most patients with FXI deficiency are mild bleeders but certain patients with similar FXI activity exhibit different bleeding phenotype. Routine laboratory assays do not help physicians to estimate the individual bleeding risk in these patients. Thrombin generation test (TGT) is a more comprehensive, global function test of the clotting system. We investigated whether or not the bleeding tendency of patients with FXI deficiency is correlated with features of the TGT. Twenty‐four patients with FXI deficiency were divided in two groups: (i) severe bleeders (n = 9) and (ii) mild or non‐bleeders (n = 15). All severe bleeders had a personal history of surgery‐related severe bleeding. Thrombin generation (TG) was measured in platelet‐rich plasma (PRP) using a low concentration of tissue factor 0.5 pm . In patients exhibiting severe bleeding tendency, independently of their FXI level, a dramatically impaired TG was observed. For example, despite a low plasma FXI = 1 IU dl^?1, a clinically non‐bleeding individual exhibited normal TG results whereas another patient with severe bleeding history and FXI = 40 IU dl^–1 had a very low TG capacity. Low velocity and delayed TG were the main parameters suggesting a higher bleeding risk. DNA analysis of patients reported eight novel mutations of the FXI gene but neither mutation location nor secretion or not of the variant correlated with the bleeding tendency. The results of this study suggest that TG measurement in PRP may be a useful tool to predict bleeding risk in FXI deficiency and should be studied further in larger prospective clinical studies.     

Optimizing warfarin reversal – an ex vivo study

Summary.  Background: Warfarin reversal is a common clinical situation. This is commonly performed using vitamin K and, depending on the urgency, fresh frozen plasma (FFP), prothrombin complex concentrates (PCCs), or activated factor VII. Even though PCCs are widely used, the ideal dosing regimen is far from established. Objectives: To verify differences in warfarin reversal patterns using FFP, recombinant FVIIa (rFVIIa), and PCC; and to test the hypothesis that supratherapeutic International Normalized Ratios (INRs) might not correlate with thrombin generation (TG) and identify the ideal concentrations of PCC required to reverse various INR thresholds. Methods: We studied the effects of FFP, rFVIIa and Beriplex  P/N on the INR and TG, using the calibrated automated thrombography assay in ex vivo warfarinized plasma. Plasmas with different INRs were spiked with different concentrations of Beriplex  P/N. Results: Beriplex  P/N was the only agent that completely normalized TG and the INR. The endogenous thrombin potential (ETP) and the peak thrombin showed a significant negative correlation with all INRs. The ETP and velocity of TG reached a plateau at an INR of ∼ 4.0. A concentration equivalent to a dose of 30 IU kg⁻¹ Beriplex  P/N normalized the ETP, the INR, FII, FVII, FIX and FX of samples with INRs  ≥ 4.0. Higher doses resulted in hypercoagulable TG patterns. A concentration equivalent to a dose of 20 IU kg⁻¹ was sufficient to reverse warfarin at an INR range of 2.0–3.9, as judged by the same tests. Conclusions: Warfarin reversal algorithms could be simplified with the adoption of this strategy utilizing two doses of PCC, depending on the INR of the patient. This would also lead to cost reductions and, possibly, a reduction in thrombotic risk.