Understanding alkali metal cation affinities of multi-layer guanine quadruplex DNA.

To gain better understanding of the stabilizing interactions between metal ions and DNA quadruplexes, dispersion-corrected density functional theory (DFT-D) based calculations were performed on double-, triple- and four-layer guanine tetrads interacting with alkali metal cations. All computations were performed in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. To facilitate the computations on these significant larger systems, optimization of the DFT description was performed first by evaluating the performance of partial reduced basis sets. Analysis of the stabilizing interactions between alkali cations and the DNA bases in double and triple-layer guanine quadruplex DNA reproduced the experimental affinity trend of the order Li+< Rb+ < Na+ < K+. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Nevertheless, for the alkali metal cation species individually, the magnitude of the bond energy stays equal for binding as first, second or third cation in double, triple and four-layer guanine quadruplexes, respectively. This is the result of an interplay between a decreasingly stabilizing interaction energy and increasingly stabilizing solvation effects, along the consecutive binding events. This diminished interaction energy is the result of destabilizing electrostatic repulsion between the hosted alkali metal cations. This work emphasizes the stabilizing effect of aqueous solvent on large highly charged biomolecules.

The role of alkali metal cations in the stabilization of guanine quadruplexes: why K(+) is the best.

The alkali metal ion affinity of guanine quadruplexes has been studied using dispersion-corrected density functional theory (DFT-D). We have done computational investigations in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. In both cases, an alkali metal cation is needed to assist self-assembly. Our quantum chemical computations on these supramolecular systems are able to reproduce the experimental order of affinity of the guanine quadruplexes for the cations Li(+), Na(+), K(+), Rb(+), and Cs(+). The strongest binding is computed between the potassium cation and the quadruplex as it occurs in nature. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Until now, the relative importance of these two factors has remained unclear and debated. By assessing the quantum chemical 'size' of the cation, determining the amount of deformation of the quadruplex needed to accommodate the cation and through the energy decomposition analysis (EDA) of the interaction energy between the cation and the guanines, we reveal that the desolvation and size of the alkali metal cation are both almost equally responsible for the order of affinity.

Reduced fibrinolytic resistance in patients with factor XI deficiency. Evidence of a thrombin-independent impairment of the thrombin-activatable fibrinolysis inhibitor pathway.

UNLABELLED: Essentials Plasma of factor XI-deficient patients (FXI-dp) displays enhanced fibrinolysis. We investigated the role of thrombin activatable fibrinolysis inhibitor (TAFI) in 18 FXI-dp. FXI-dp generated less activated TAFI (TAFIa) on clotting challenge and were resistant to TAFIa. TAFI activation and TAFIa resistance correlated with bleeding score and bleeding phenotype. SUMMARY: Background Factor XI (FXI) deficiency, a rare disorder with unpredictable bleeding, has been associated with reduced fibrinolytic resistance as a result of abnormal fibrin density. Objective We investigated the involvement of thrombin-activatable fibrinolysis inhibitor (TAFI) in the increased lysability of FXI-deficient (FXI-def) clots and the role of thrombin. Patients/Methods Eighteen patients with FXI deficiency (1-58%) and 17 matched controls were investigated for fibrinolytic resistance to t-PA, thrombin generation, TAFI activation and response to TAFIa. Results When clotting was induced by 0.5 pm tissue factor (TF), FXI-def plasmas displayed less thrombin and TAFIa generation and shorter lysis time than controls. A 100-fold higher TF concentration (to bypass FXI) abolished the difference in thrombin generation but not in lysis time between patients and controls. Normalization of FXI levels by a FXI concentrate increased thrombin generation but had no effect on the lysis time of FXI-def plasma. Moreover, when clots were induced by purified thrombin and high concentrations of FXa inhibitor, FXI-def plasma still generated less TAFIa and displayed a shorter lysis time than controls. Finally, upon TAFIa addition, the lysis time of FXI-def plasma was prolonged significantly less than that of control plasma, suggesting a TAFIa resistance. TAFIa generation and TAFIa resistance were correlated with the bleeding score, displaying a considerable capacity to discriminate between patients with and without bleeding. Conclusions TAFI pathway impairment, largely caused by a hitherto unknown TAFIa resistance, appears to be one main cause of decreased fibrinolytic resistance in FXI deficiency and might be clinically useful for assessing the bleeding risk of FXI-def patients.

High-dose aprotinin modulates the balance between proinflammatory and anti-inflammatory responses during coronary artery bypass graft surgery.

OBJECTIVE: To rule out the effect of high-dose aprotinin in respect to the balance of proinflammatory and anti-inflammatory mediators induced by cardiopulmonary bypass (CPB). DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: University-affiliated cardiac center. PARTICIPANTS: Twenty patients scheduled for coronary artery bypass graft surgery. INTERVENTIONS: In group A patients (n = 10), high-dose aprotinin was administered (2 x 106 KIU pre-CPB, 2 x 10(6) KIU in prime, 500,000 KIU/hr during CPB). In group C patients (n = 10), placebo was used instead. Proinflammatory interleukin (IL)-6, anti-inflammatory IL-1-receptor antagonist, and clinical parameters were measured 8 times perioperatively. The values are presented as mean +/- SEM. MEASUREMENTS AND MAIN RESULTS: Four hours after CPB, IL-6 concentration reached the maximum value, being significantly lower in group A patients as compared with group C patients (615 +/- 62 pg/mL v 1,409 +/- 253 pg/mL; p = 0.019). On the first postoperative day, the concentration of IL-6 in group A patients remained lower (219 +/- 24 pg/mL v 526 +/- 123 pg/mL; p = 0.015). In contrast, IL-1-receptor antagonist concentration was higher in group A patients as compared with group C patients after CPB (13,857 +/- 4,264 pg/mL v 5,675 +/- 1,832 pg/mL; p = 0.03). Total postoperative blood loss was lower in group A patients as compared with group C patients (648 +/- 64 mL v 1,284 +/- 183 mL; p = 0.002). CONCLUSIONS: High-dose aprotinin treatment reduced the inflammatory reaction and postoperative blood loss. The anti-inflammatory reaction was significantly enhanced in these patients, which suggests that the physiologic reaction of the organism to reduce the deleterious effects from CPB is more pronounced by using high-dose aprotinin.

Hemodynamic alterations during massive incisional hernioplasty.

BACKGROUND: The operative treatment of a large abdominal incisional hernia increases intra-abdominal pressure (IAP). This study was done to verify if this IAP elevation acts on the cardiocirculatory function. STUDY DESIGN: Hemodynamic measurements were performed in five patients who underwent massive incisional hernioplasty before and after abdominal wall closure. RESULTS: Reduction of a large abdominal hernia increases (+226 percent) IAP, which can produce serious hemodynamic alterations, manifested in two patients by a fall of cardiac output (-30 percent), without significant variations of heart rate and arterial pressure. Cardiac output is decreased secondary to decreased venous return, despite the increase in measured central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP). CONCLUSIONS: During massive incisional hernioplasty, CVP cannot be used as an indicator of venous return to the heart as it reflects a composite of venous filling pressure, pleural pressure, and transmitted IAP. Transmural CVP and PCWP, and not directly measured CVP and PCWP, should be used as clinical indicators of venous return to the heart in this situation.

Atrial fibrillation and infarct area extent in ischemic stroke. A clinical and neuroradiological study in 104 patients.

The extent of infarct area (IA) on CT-scan in 104 patients with ischemic stroke (IS) was compared with the presence of atrial fibrillation (AF) and other risk factors (hypertension, dyslipidemia, alcohol abuse). Infarct size was also compared with biological and clinical parameters in acute stage (6-12 h) (blood glucose level, systolic and diastolic arterial pressure, haematocrit, consciousness, clinical picture) and with clinical outcome. Among risk factors, only AF showed a significant correlation with IA extension (p less than .0009). IA correlated also with consciousness (p = .0017), clinical picture (p = .0145) and with clinical outcome (p less than 10(-6). Patients with AF showed a more severe clinical outcome with respect to patients without risk factors. It could be hypothesized that patients with AF have a reduced capacity for increasing or sustaining cerebral blood flow in the acute phase of IS.

[Immunologic changes in chronic pancreatitis]. / Alterazioni immunologiche nella pancreatite cronica.

In 35 patients with chronic pancreatitis, C3, C4, s-immunoglobulins, circulating immunocomplexes and T-lymphocytes were assessed in order to verify whether an immunological role may be postulated in the pathogenesis and/or in the maintenance of the disease. A significant increase of serum IgM together with normal values of C3 and C4 and without circulating immunocomplexes was found. A significant decrease in the total number of lymphocytes as well as in the number and percentage of T-lymphocytes was also documented. These results suggest a possible involvement of immunological (humoral and cellular) processes in maintaining the chronic pancreatic damage.