Influence of Charged Polypeptides on Nucleation and Growth of CaCO₃ Evaluated by Counterdiffusion Experiments

Many mineralization processes occur in convection-free conditions. Understanding these processes requires knowledge of crystal nucleation and growth processes in gels or high viscous sol systems. In this work, the crystallization parameters of calcium carbonate in an agarose viscous sol using counterdiffusion crystallization were monitored as a function of time. Additionally, by comparing the precipitation parameters in the high viscous sol entrapping charged polypeptides, namely, poly-l-lysine (pLys), poly-l-aspartate (pAsp), and poly-l-glutamate (pGlu), it was possible to establish the polypeptide capability to inhibit, or eventually promote, the calcium carbonate nucleation and/or crystal growth processes. The polymorphism and morphology of the precipitates indicate that pLys only influences the growth mechanism of calcium carbonate without affecting the nucleation process. On the contrary, pAsp and, to a minor extent, pGlu affect both nucleation and growth. The application of this analysis can be extended to other additives and macromolecules able to affect crystallization processes

Clinical outcomes after discontinuing anticoagulant therapy in patients with first unprovoked venous thromboembolism

Background: The duration of anticoagulation for a first episode of unprovoked venous thromboembolism (VTE) should balance the likelihood of VTE recurrence against the risk of major bleeding. Objectives: Analyze rates and case-fatality rates (CFRs) of recurrent VTE and major bleeding after discontinuing anticoagulation in patients with a first unprovoked VTE after at least 3 months of anticoagulation. Methods: We compared the rates and CFRs in patients of the Registro Informatizado Enfermedad Trombo Embólica (RIETE) and Contemporary management and outcomes in patients with venous thromboembolism registries. We used logistic regression models to identify predictors for recurrent pulmonary embolism (PE) and major bleeding. Results: Of 8261 patients with unprovoked VTE in RIETE registry, 4012 (48.6%) had isolated deep vein thrombosis (DVT) and 4250 had PE. Follow-up (median, 318 days) showed 543 recurrent DVTs, 540 recurrent PEs, 71 major bleeding episodes, and 447 deaths. The Contemporary management and outcomes in patients with venous thromboembolism registry yielded similar results. Corresponding CFRs of recurrent DVT, PE, and major bleeding were 0.4%, 4.6%, and 24%, respectively. On multivariable analyses, initial PE presentation (hazard ratio [HR], 3.03; 95% CI, 2.49-3.69), dementia (HR, 1.47; 95% CI, 1.01-2.13), and anemia (HR, 0.72; 95% CI, 0.57-0.91) predicted recurrent PE, whereas older age (HR, 2.11; 95% CI, 1.15-3.87), inflammatory bowel disease (HR, 4.39; 95% CI, 1.00-19.3), and anemia (HR, 2.24; 95% CI, 1.35-3.73) predicted major bleeding. Prognostic scores were formulated, with C statistics of 0.63 for recurrent PE and 0.69 for major bleeding. Conclusion: Recurrent DVT and PE were frequent but had low CFRs (0.4% and 4.6%, respectively) after discontinuing anticoagulation. On the contrary, major bleeding was rare but had high CFR (24%). A few clinical factors may predict these outcomes