Magnesium(II) is a crucial constituent of the blood coagulation cascade. Potentiation of coagulant activities of factor IX by Mg2+ ions

A specific fluorescence resonance energy quenching-based biosensor for measuring thrombin activity in whole blood

BACKGROUND

At sites of vessel injury, thrombin acts as the central mediator of coagulation by catalyzing fibrin clot formation and platelet activation. Thrombin generation is most frequently measured in plasma samples using small-molecule substrates; however, these have low specificity for thrombin and limited utility in whole blood. Plasma assays are limited because they ignore the hemostatic contributions of blood cells and require anticoagulation and the addition of supraphysiological concentrations of calcium.

OBJECTIVES

To overcome these limitations, we designed and characterized a fluorescence resonance energy quenching-based thrombin sensor (FTS) protein.

METHODS

The fluorescence resonance energy quenching pair of mAmetrine and tTomato, separated by a thrombin recognition sequence, was developed. The protein was expressed using Escherichia coli, and purity was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The cleavage of FTS was monitored by fluorescence using excitation at 406 nm and emission at 526 nm and 581 nm.

RESULTS

Compared with small-molecule substrates, the FTS demonstrated high specificity for thrombin; it is not cleaved by thrombin or inhibited by α2-macroglobulin and interacts with thrombin's anion-binding exosite I. The FTS can effectively measure thrombin generation in plasma and in finger-prick whole blood, which allows it to be developed into a point-of-care test of thrombin generation. The FTS does not inhibit standard thrombin-generation assays. Lastly, FTS-based thrombin generation in nonanticoagulated finger-prick blood was delayed but enhanced compared with that in citrated plasma.

CONCLUSION

The FTS will broaden our understanding of thrombin generation in ways that are not attainable with current methods.

Potential Drug-Nutrient Interactions of 45 Vitamins, Minerals, Trace Elements, and Associated Dietary Compounds with Acetylsalicylic Acid and Warfarin-A Review of the Literature

In cardiology, acetylsalicylic acid (ASA) and warfarin are among the most commonly used prophylactic therapies against thromboembolic events. Drug-drug interactions are generally well-known. Less known are the drug-nutrient interactions (DNIs), impeding drug absorption and altering micronutritional status. ASA and warfarin might influence the micronutritional status of patients through different mechanisms such as binding or modification of binding properties of ligands, absorption, transport, cellular use or concentration, or excretion. Our article reviews the drug-nutrient interactions that alter micronutritional status. Some of these mechanisms could be investigated with the aim to potentiate the drug effects. DNIs are seen occasionally in ASA and warfarin and could be managed through simple strategies such as risk stratification of DNIs on an individual patient basis; micronutritional status assessment as part of the medical history; extensive use of the drug-interaction probability scale to reference little-known interactions, and application of a personal, predictive, and preventive medical model using omics.

Nanoapatite-Loaded κ-Carrageenan/Poly(vinyl alcohol)-Based Injectable Cryogel for Hemostasis and Wound Healing

Immediate control of excessive bleeding and prevention of infections are of utmost importance in the management of wounds. Cryogels have emerged as promising materials for the rapid release of medication and achieving hemostasis. However, their quick release properties pose the challenge of exposing patients to high concentrations of drugs. In this study, hybrid nanocomposites were developed to address this issue by combining poly(vinyl alcohol) and κ-carrageenan with whitlockite nanoapatite (WNA) particles and ciprofloxacin, aiming to achieve rapid hemostasis and sustained antibacterial effects. A physically cross-linked cryogel was obtained by subjecting a blend of poly(vinyl alcohol) and κ-carrageenan to successive freezing-thawing cycles, followed by the addition of WNA. Furthermore, ciprofloxacin was introduced into the cryogel matrix for subsequent evaluation of its wound healing properties. The resulting gel system exhibited a 3D microporous structure and demonstrated excellent swelling, low cytotoxicity, and outstanding mechanical properties. These characteristics were evaluated through analytical and rheological experiments. The nanocomposite cryogel with 4% whitlockite showed extended drug release of 71.21 ± 3.5% over 21 days and antibacterial activity with a considerable growth inhibition zone (4.19 ± 3.55 cm). Experiments on a rat model demonstrated a rapid hemostasis property of cryogels within an average of 83 ± 4 s and accelerated the process of wound healing with 96.34% contraction compared to the standard, which exhibited only ∼78% after 14 days. The histopathological analysis revealed that the process of epidermal re-epithelialization took around 14 days following the skin incision. The cryogel loaded with WNAs and ciprofloxacin holds great potential for strategic utilization in wound management applications as an effective material for hemostasis and anti-infection purposes.

Trace Metals and The Hemostatic System

In this narrative review we report the main relationships between trace metals and the hemostatic system since this aspect has seldom attracted the attention of the scientific community. A basic aspect to be considered is the importance of maintaining the fine control of all trace metals' levels since they have an important impact on the pathophysiology of the hemostatic system. It is worth noting that poor diet habits are responsible for most trace metal deficiencies, while pollution is responsible for dangerous exposure to them with a consequent negative impact on the general population. This appears of paramount importance in planning the implementation of food and nutrient support to ameliorate the hidden hunger and the quality of life of people especially in developing countries and limiting poisons both in the air and food. As it often happens, when damage to certain mechanisms takes a very long time to appear, no attention is paid to the importance of a systematic prevention to avoid late negative outcomes.

Association of Serum Magnesium with Gastrointestinal Bleeding in Peritoneal Dialysis Patients: a Multicentre Retrospective Study

Serum magnesium is involved in the process of blood coagulation, and low serum magnesium is associated with haemorrhagic diseases. No studies have explored the relationship between serum magnesium and gastrointestinal bleeding (GIB). This study aimed to explore the association between serum magnesium and GIB in peritoneal dialysis (PD) patients. This was a multicentre retrospective cohort study. The primary endpoint was GIB. According to the baseline serum magnesium level of 0.7 mmol/L, patients were divided into two groups: the hypomagnesaemia group and the nonhypomagnesaemia group. A multivariate Cox regression model was used to investigate the association between hypomagnesaemia and GIB. A total of 654 PD patients from four Chinese peritoneal dialysis centres were recruited from February 1, 2010 to January 31, 2020. During the follow-up, 47 patients experienced GIB. Kaplan-Meier curves showed that there was a significant difference in the risk of GIB between the two groups (log-rank = 11.82, P < 0.001). The multivariable Cox regression model showed that the risk of GIB was higher in the hypomagnesaemia group than the nonhypomagnesaemia group after adjustment for demographic variables and laboratory indicators (HR = 3.007, 95% CI 1.488-6.079, P = 0.002). A baseline lower serum magnesium level was associated with a higher risk of GIB in PD patients.

Magnesium Deficiency and Cardiometabolic Disease

Magnesium (Mg²⁺) has many physiological functions within the body. These include important roles in maintaining cardiovascular functioning, where it contributes to the regulation of cardiac excitation-contraction coupling, endothelial functioning and haemostasis. The haemostatic roles of Mg²⁺ impact upon both the protein and cellular arms of coagulation. In this review, we examine how Mg²⁺ homeostasis is maintained within the body and highlight the various molecular roles attributed to Mg²⁺ in the cardiovascular system. In addition, we describe how nutritional and/or disease-associated magnesium deficiency, seen in some metabolic conditions, has the potential to influence cardiac and vascular outcomes. Finally, we also examine the potential for magnesium supplements to be employed in the prevention and treatment of cardiovascular disorders and in the management of cardiometabolic health.

The Effect of Serum Magnesium Level on Stable Anticoagulation in Patients Using Warfarin for Various Cardiac Indications

Warfarin is a vitamin K antagonist agent that inhibits clotting factors used for long-term anticoagulation. Time in therapeutic range (TTR) in patients using warfarin is one of the primary treatment effectiveness requirements. We aim to investigate the relationship between serum magnesium levels, the international normalized ratio (INR) values, and TTR values in people using warfarin for various indications. Our study is a single-center, cross-sectional, and retrospective study that included 169 patients between 18 and 70 who used warfarin for various indications. Demographic data, biochemical analysis, and coagulation parameters, including TTR calculation, were evaluated for all patients. Those with a TTR value below 60 were defined as labile INR, and those with 60 and above as stable INR group and compared. The mean INR value was higher in the labile INR group than the stable INR group (3.7 ± 2.9, 3.2 ± 0.3, respectively; p = 0.030). The Mg values are significantly lower in the labile INR group than the stable group (1.8 ± 0.2 mg/dL, 2.0 ± 0.1 mg/dL, respectively; p < 0.001). In binary multivariate logistic regression analysis, magnesium value was the most influential INR stabilization factor (p < 0.001). As a result of our study, it was concluded that magnesium levels are an influential factor in stabilizing INR. We can state that we have contributed to the literature and can be a reference for future studies.

A Review on the Recent Advancements on Therapeutic Effects of Ions in the Physiological Environments

This review focuses on the therapeutic effects of ions when released in physiological environments. Recent studies have shown that metallic ions like Ag+, Sr2+, Mg2+, Mn2+, Cu2+, Ca2+, P+5, etc., have shown promising results in drug delivery systems and regenerative medicine. These metallic ions can be loaded in nanoparticles, mesoporous bioactive glass nanoparticles (MBGNs), hydroxyapatite (HA), calcium phosphates, polymeric coatings, and salt solutions. The metallic ions can exhibit different functions in the physiological environment such as antibacterial, antiviral, anticancer, bioactive, biocompatible, and angiogenic effects. Furthermore, the metals/metalloid ions can be loaded into scaffolds to improve osteoblast proliferation, differentiation, bone development, fibroblast growth, and improved wound healing efficacy. Moreover, different ions possess different therapeutic limits. Therefore, further mechanisms need to be developed for the highly controlled and sustained release of these ions. This review paper summarizes the recent progress in the use of metallic/metalloid ions in regenerative medicine and encourages further study of ions as a solution to cure diseases.

Nanoporous and nano thickness film-forming bioactive composition for biomedical applications

Unmanageable bleeding is one of the significant causes of mortality. Attaining rapid hemostasis ensures subject survivability as a first aid during combats, road accidents, surgeries that reduce mortality. Nanoporous fibers reinforced composite scaffold (NFRCS) developed by a simple hemostatic film-forming composition (HFFC) (as a continuous phase) can trigger and intensify hemostasis. NFRCS developed was based on the dragonfly wing structure's structural design. Dragonfly wing structure consists of cross-veins and longitudinal wing veins inter-connected with wing membrane to maintain the microstructural integrity. The HFFC uniformly surface coats the fibers with nano thickness film and interconnects the randomly distributed cotton gauge (Ct) (dispersed phase), resulting in the formation of a nanoporous structure. Integrating continuous and dispersed phases reduce the product cost by ten times that of marketed products. The modified NFRCS (tampon or wrist band) can be used for various biomedical applications. The in vivo studies conclude that the developed Cp NFRCS triggers and intensifies the coagulation process at the application site. The NFRCS could regulate the microenvironment and act at the cellular level due to its nanoporous structure, which resulted in better wound healing in the excision wound model.

Recent advances in the production of recombinant factor IX: bioprocessing and cell engineering

Appropriate treatment of Hemophilia B is vital for patients' quality of life. Historically, the treatment used was the administration of coagulation Factor IX derived from human plasma. Advancements in recombinant technologies allowed Factor IX to be produced recombinantly. Successful recombinant production has triggered a gradual shift from the plasma derived origins of Factor IX, as it provides extended half-life and expanded production capacity. However, the complex post-translational modifications of Factor IX have made recombinant production at scale difficult. Considerable research has therefore been invested into understanding and optimizing the recombinant production of Factor IX. Here, we review the evolution of recombinant Factor IX production, focusing on recent developments in bioprocessing and cell engineering to control its post-translational modifications in its expression from Chinese Hamster Ovary (CHO) cells.

Accelerating skin barrier repair using novel bioactive magnesium-doped nanofibers of non-mulberry silk fibroin during wound healing

Novel magnesium doped non-mulberry silk fibroin nanofibers with ability to enhance skin barrier function were successfully fabricated using electrospinning technique for wound healing applications. Magnesium nanoparticles incorporated in the electrospun nanofibers releases Mg2+ ions at the site of implementation. The effect of Mg2+ is of considerable concern in wound healing due to its skin barrier repair ability and its role in blood coagulation. The physicochemical characterization of the scaffold was investigated by determining the morphology and secondary structure confirmation. The effects of Mg2+ ions in silk fibroin microenvironment have been evaluated using SEM, XRD, and FTIR to confirm the incorporation of magnesium in the film. The aim of this study is to see the effect of doped Mg on the structural, physical, and biological properties of non-mulberry silk fibroin (NSF) film. The magnesium doped nanofibrous film exhibited enhanced mechanical property, satisfactory blood clotting ability, and good in vitro degradability. This silk fibroin-based film mimicking extracellular matrix for skin regeneration were constructed using electrospinning technique. The wound healing efficiency of prepared nanofibers were evaluated in full-thickness wound models of rat. The Mg doped silk fibroin film exhibited faster wound healing activity (14 days) among all experimental group. The study indicates the potential of magnesium-doped silk /PVA film as skin substitute film.

Blood Products, Crystalloids, and Rapid Infusion: An Experimental Study With Magnesium

OBJECTIVES

Calcium and magnesium are concentration-dependent pro- and anticoagulant cofactors, and magnesium behaves similarly to calcium in the presence of citrate. The authors hypothesized that magnesium can cause clot formation (primary objective) when mixed with coagulation factor-containing blood products diluted with different crystalloids in a rapid- infuser reservoir. A secondary objective was the observation of any infuser alarms and stops in the event of clotting.

DESIGN

An experimental in vitro study with blood products, crystalloids, magnesium, and calcium in a rapid infuser with a reservoir using a closed-loop system.

SETTING

Anesthesia research laboratory at an urban academic tertiary medical center PARTICIPANTS: Not applicable.

INTERVENTIONS

Exposure of fresh frozen plasma (FFP) and packed red blood cells alone (control) or in combination with either normal saline (NS), lactated Ringer's solution (LR), or Plasma-Lyte A (PL) to increasing concentrations of magnesium sulphate (MgSO₄) up to 1 g. After each incremental MgSO₄ change, the authors applied a specific pump-flow sequence in a closed-loop system with a rapid-infuser reservoir, and if no clot was observed, the authors incrementally added calcium chloride (CaCl₂) up to 1 g.

MEASUREMENTS AND MAIN RESULTS

Observation of macroscopic clot and time to event, as well as occurrence and type of any pump alarms or stops. LR experiments resulted in clot observation in the reservoir by a dedicated observer after MgSO₄ 275 ± 206 mg (95% confidence interval [CI], 9-541). Adding MgSO₄ 1 g in the NS, PL, or the control experiments did not result in clot observation. Only when CaCl₂ 166.7 ± 51.64 mg (95% CI, 112.0-22.01) was added to the combination of blood products alone or mixed with NS and PL, clotting occurred. The mean FFP volume was 281 ± 48.6 mL (range, 204-340 mL) and was not different between groups (p = 0.44). Pump alarms and stops were inconsistent.

CONCLUSIONS

The addition of magnesium to a combination of LR with coagulation factor- containing blood products consistently resulted in a visible blood clot in the rapid-infuser reservoir in the authors' experimental setup. In addition to MgSO₄ 1 g in the control, NS, and PL experiments, CaCl₂ is needed before a clot can be observed.

The impact of environmental and occupational exposures of manganese on pulmonary, hepatic, and renal functions

Manganese (Mn) is an essential trace element for humans, but long-term environmental or occupational exposures can lead to numerous health problems. Although many studies have identified an association between Mn exposures and neurological abnormalities, emerging data suggest that occupationally and environmentally relevant levels of Mn may also be linked to multiple organ dysfunction in the general population. In this regard, many experimental and clinical studies provide support for a causal link between Mn exposure and structural and functional changes that are responsible for organ dysfunction in major organs like lung, liver, and kidney. The underlying mechanisms suggested to Mn toxicity include altered activities of the components of intracellular signaling cascades, oxidative stress, apoptosis, affected cell cycle regulation, autophagy, angiogenesis, and an inflammatory response. We further discussed the sources and possible mechanisms of Mn absorption and distribution in different organs. Finally, treatment strategies available for treating Mn toxicity as well as directions for future studies were discussed.

Association of Low Magnesium Level With Duration and Severity of Type 2 Diabetes

Introduction: Type 2 diabetes mellitus can give rise to several complications in the body, including electrolyte imbalance. In this study, we aim to find the association of hypomagnesemia with the duration and severity of diabetes. Understanding the association between magnesium and diabetes may assist in the early detection of hypomagnesemia and help manage the complications associated with electrolyte imbalance.

Methods: This cross-sectional study was conducted in the internal medicine department of a tertiary care hospital in Pakistan from January to March 2021. Three hundred (n = 300) patients with a confirmed diagnosis of type 2 diabetes were enrolled in the study after informed consent via consecutive convenient non-probability sampling. Three hundred (n = 300) patients were included in the study as a reference group. Blood was drawn via phlebotomy and sent to the laboratory to assess glycated hemoglobin (HbA1c) and magnesium levels.

Results: In uncontrolled diabetic patients, mean magnesium level was significantly lower as compared to diabetic patients with good glycemic control (1.34 ± 0.3 mg/dL vs. 1.81 ± 0.5; p-value: <0.0001). Prevalence of hypomagnesemia was significantly more in patients with uncontrolled diabetes, compared to the controlled diabetic group (65.8% vs. 50.8%; p-value: 0.009). In patients with a duration of diabetes of more than 10 years, the mean magnesium level was significantly lower, compared to patients with less than 10 years of diabetes (1.32 ± 0.3 mg/dL vs. 1.78 ± 0.5; p-value: <0.0001). Prevalence of hypomagnesemia was significantly more in patients with diabetes for more than 10 years (64.7% vs. 51.9%; p-value: 0.02).

Conclusion: Hypomagnesemia is prevalent in diabetes and is directly related to the severity and duration of diabetes. It is important to include electrolyte screening as a part of routine screening in diabetic patients for early detection and management of electrolyte imbalance, including hypomagnesemia.

Association between electrolyte levels at presentation and hematoma expansion and outcome in spontaneous intracerebral hemorrhage: A systematic review

PURPOSE

To assess the association between specific electrolyte levels (sodium, potassium, calcium, magnesium, and phosphorus) on presentation and hematoma expansion (HE) and outcome in intracerebral hemorrhage (ICH).

METHODS

This review was conducted in accordance with the PRISMA statement recommendations. Three databases were searched (Pubmed, Scopus, and Cochrane). Risk of bias was computed using the Newcastle-Ottawa Scale tool.

RESULTS

18 full-text articles were included in this systematic review including 10,385 ICH patients. Hypocalcemia was associated with worse short-term outcome in four studies, and two other studies were neutral. All studies investigating HE in hypocalcemia (n = 5) reported an association between low calcium level and HE. Hyponatremia (Na < 135 mEq/L) was shown to correlate with worse short-term outcome in two studies, and worse long-term outcome in one. There was one report showing no association between sodium level and HE. Hypomagnesemia was shown to be associated with worse short-term outcome in one study, while other reports were neutral. Studies evaluating hypophosphatemia or hypokalemia in ICH were limited, with no demonstrable significant effect on outcome.

CONCLUSION

This review suggests a significant association between hypocalcemia, hyponatremia and, of lesser degree, hypomagnesemia on admission and HE or worse outcome in ICH.

Magnesium and Risk of Bleeding Complications From Ventriculostomy Insertion

BACKGROUND AND PURPOSE

Hemorrhages are a serious complication of brain surgery, and magnesium has shown hemostatic properties in hemorrhagic stroke and non-neurological surgeries. External ventricular drain (EVD) insertion is an advantageous model of emergency neurosurgical hemorrhage risk because it is common, standardized, and the operator is blinded to the outcome during the procedure. We tested the hypothesis that low magnesium is associated with risk of hemorrhagic complications from EVD insertion.

METHODS

Patients with spontaneous intracerebral hemorrhage and aneurysmal subarachnoid hemorrhage were enrolled in a prospective, observational study. Demographic and clinical variables were prospectively recorded, including serum magnesium measurements. Catheter tract hemorrhage (CTH) was measured on postoperative head computed tomography within 48 hours of EVD insertion.

RESULTS

We observed 50 CTH among 327 EVD procedures (15.3%) distributed similarly among intracerebral hemorrhage (21/116 [18.1%]) and subarachnoid hemorrhage (29/211 [13.7%]). Magnesium was lower in patients with CTH compared with those without (median 1.8 versus 2.0 mg/dL, P<0.0001). Higher magnesium was associated with lower odds of CTH (odds ratio 0.67 per 0.1 mg/dL magnesium [95% CI, 0.56-0.78], P<0.0001) after adjustment for other risk factors, with similar effect in the intracerebral hemorrhage and subarachnoid hemorrhage subgroups. Preprocedural increase in magnesium (odds ratio 0.68 [0.52-0.85]) and dose of preprocedural magnesium sulfate (odds ratio 0.67 [0.40-0.97]) were associated with reduced CTH risk after adjustment for initial magnesium and other risk factors.

CONCLUSIONS

Lower magnesium at the time of EVD insertion was an independent predictor of hemorrhagic complications. Baseline risk was attenuated by preprocedural increases in magnesium, suggesting a therapeutic opportunity.

Magnesium Therapy Improves Rotational Thromboelastometry Findings Prior to Liver Transplantation: A Randomized Clinical Trial

An important challenge during orthotopic liver transplantation (OLT) is optimal coagulation management. There are diverse studies regarding effect of Mg sulfate on coagulation system. This study evaluates the impact of Mg sulfate on the coagulation parameters of the rotational thromboelastometry (ROTEM) in patients about to undergo OLT. In this randomized clinical trial, 60 patients who were going to undergo OLT were randomly allocated into two groups. In the Mg group, the patients received a 1.5 g infusion of Mg 5 min before the surgical incision. In the control group, patients received a physiological saline instead of Mg. Plasma Mg levels before and after the infusions were measured in both groups. Also, three ROTEM tests: EXTEM, INTEM and FIBTEM were performed before and after the infusions. Baseline mean plasma magnesium levels were within normal range in the control and Mg groups: 2.06 and 2.18 mg/dl, respectively. After magnesium therapy, the mean plasma Mg level in the Mg group increased to 2.78 mg/dl in compared to the control group that was 2.01 mg/dl (P < 0.000). Mean value of the clotting time (CT) in the magnesium group were significantly decreased from 129.50 ± 7.76, 381.86 ± 8.51 and 114.26 ± 6.80 to 86.13 ± 3.4, 209.33 ± 6.68 and 81.56 ± 5.01 in the EXTEM, INTEM, and FIBTEM respectively after intervention in the Mg group (P = 0.001). Among patients with end-stage liver diseases who have ROTEM evidence of hypocoagulability, magnesium could correct CT parameter of the ROTEM tests.

Reduced Plasma Magnesium Levels in Type-1 Diabetes Associate with Prothrombotic Changes in Fibrin Clotting and Fibrinolysis

Individuals with type-1 diabetes mellitus (T1DM) have a higher risk of thrombosis and low plasma magnesium concentrations. As magnesium is a known regulator of fibrin network formation, we investigated potential associations between fibrin clot properties and plasma magnesium concentrations in 45 individuals with T1DM and 47 age- and sex-matched controls without diabetes. Fibrin clot characteristics were assessed using a validated turbidimetric assay and associations with plasma magnesium concentration were examined. Plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and lipids were measured and fibrin fiber diameters assessed using scanning electron microscopy. Fibrin clot maximum absorbance was unchanged in subjects with T1DM compared with controls, while lysis time was prolonged (p = 0.0273). No differences in fibrin fiber diameters or in lipid profile were observed between T1DM and controls. PAI-1 concentration was lower in the T1DM group compared with the controls (p = 0.0232) and positively correlated with lysis time (p = 0.0023). Plasma magnesium concentration was lower in the T1DM group compared with controls (p < 0.0001). Magnesium concentration negatively correlated with clot maximum absorbance (p = 0.0215) and lysis time (p = 0.0464). A turbidimetric fibrin clot lysis assay performed in a purified system that included PAI-1 and 0 to 3.2 mM Mg2+ showed a shortening of lysis time with increasing Mg2+ concentrations (p = 0.0004). Our findings reveal that plasma magnesium concentration is associated with changes in fibrin clot and lysis parameters.

Magnesium and Hemorrhage Volume in Patients With Aneurysmal Subarachnoid Hemorrhage

OBJECTIVES

We tested the hypothesis that admission serum magnesium levels are associated with extent of hemorrhage in patients with aneurysmal subarachnoid hemorrhage.

DESIGN

Single-center prospective observational study.

SETTING

Tertiary hospital neurologic ICU.

PATIENTS

Patients with aneurysmal subarachnoid hemorrhage.

INTERVENTIONS

Clinically indicated CT scans and serum laboratory studies.

MEASUREMENTS AND MAIN RESULTS

Demographic, clinical, laboratory, and radiographic data were analyzed. Extent of initial hemorrhage was graded semi-quantitatively on admission CT scans using the modified Fisher scale (grades: 0, no radiographic hemorrhage; 1, thin [< 1 mm in depth] subarachnoid hemorrhage; 2, thin subarachnoid hemorrhage with intraventricular hemorrhage; 3, thick [≥ 1 mm] subarachnoid hemorrhage; 4, thick subarachnoid hemorrhage with intraventricular hemorrhage). We used both ordinal (modified Fisher scale) and dichotomized (thick vs thin subarachnoid hemorrhage) univariate and adjusted logistic regression models to assess associations between serum magnesium and radiographic subarachnoid hemorrhage severity. Data from 354 patients (mean age 55 ± 14 yr, 28.5% male, median admission Glasgow Coma Scale 14 [10-15]) were analyzed. Mean magnesium was lower in patients with thick versus thin subarachnoid hemorrhage (1.92 vs 1.99 mg/dL; p = 0.022). A monotonic trend across categories of modified Fisher scale was found using analysis of variance and Spearman rank correlation (p = 0.015 and p = 0.008, respectively). In adjusted ordinal and binary regression models, lower magnesium levels were associated with higher modified Fisher scale (odds ratio 0.33 per 1 mg/dL increase; 95% CI, 0.14-0.77; p = 0.011) and with thick subarachnoid hemorrhage (odds ratio 0.29 per 1 mg/dL increase; 95% CI, 0.10-0.78; p = 0.015).

CONCLUSIONS

These data support the hypothesis that magnesium influences hemorrhage severity in patients with aneurysmal subarachnoid hemorrhage, potentially through a hemostatic mechanism.

Coagulatory Defects in Type-1 and Type-2 Diabetes

Diabetes (both type-1 and type-2) affects millions of individuals worldwide. A major cause of death for individuals with diabetes is cardiovascular diseases, in part since both types of diabetes lead to physiological changes that affect haemostasis. Those changes include altered concentrations of coagulatory proteins, hyper-activation of platelets, changes in metal ion homeostasis, alterations in lipid metabolism (leading to lipotoxicity in the heart and atherosclerosis), the presence of pro-coagulatory microparticles and endothelial dysfunction. In this review, we explore the different mechanisms by which diabetes leads to an increased risk of developing coagulatory disorders and how this differs between type-1 and type-2 diabetes.

Sodium-site in serine protease domain of human coagulation factor IXa: evidence from the crystal structure and molecular dynamics simulations study

Essentials Consensus sequence and biochemical data suggest a Na+ -site in the factor (F) IXa protease domain. X-ray structure of the FIXa EGF2/protease domain at 1.37 Å reveals a Na+ -site not observed earlier. Molecular dynamics simulations data support that Na+  ± Ca2+ promote FIXa protease domain stability. Sulfate ions found in the protease domain mimic heparin sulfate binding mode in FIXa. SUMMARY: Background Activated coagulation factor IX (FIXa) consists of a γ-carboxyglutamic acid domain, two epidermal growth factor-like (EGF) domains, and a C-terminal protease domain. Consensus sequence and biochemical data support the existence of a Na+ -site in the FIXa protease domain. However, soaking experiments or crystals grown in high concentration of ammonium sulfate did not reveal a Na+ -site in wild-type or mutant FIXa EGF2/protease domain structure. Objective Determine the structure of the FIXa EGF2/protease domain in the presence of Na+ ; perform molecular dynamics (MD) simulations to explore the role of Na+ in stabilizing FIXa structure. Methods Crystallography, MD simulations, and modeling heparin binding to FIXa. Results Crystal structure at 1.37-Å resolution revealed that Na+ is coordinated to carbonyl groups of residues 184A, 185, 221A, and 224 in the FIXa protease domain. The Na+ -site in FIXa is similar to that of FXa and is linked to the Asp189 S1-site. In MD simulations, Na+ reduced fluctuations in residues 217-225 (Na+ -loop) and 70-80 (Ca2+ -loop), whereas Ca2+ reduced fluctuations only in residues of the Ca2+ -loop. Ca2+ and Na+ together reduced fluctuations in residues of the Ca2+ -loop and Na+ -loop (residues 70-80, 183-194, and 217-225). Moreover, we observed four sulfate ions that make salt bridges with FIXa protease domain Arg/Lys residues, which have been implicated in heparin binding. Based upon locations of the sulfate ions, we modeled heparin binding to FIXa, which is similar to the heparin binding in thrombin. Conclusions The FIXa Na+ -site in association with Ca2+ contributes to stabilization of the FIXa protease domain. The heparin binding mode in FIXa is similar to that in thrombin.

Serum magnesium level and hematoma expansion in patients with intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is a devastating subtype of stroke that results in significant rates of mortality and morbidities. The initial hematoma volume, hematoma expansion (HE), blood pressure (BP), and coagulopathy are considered strong predictors of clinical outcomes and mortality. Low serum magnesium (Mg⁺⁺) levels have been shown to be associated with larger initial hematoma and greater HE. Coagulopathy, platelet dysfunction, high BP, and increased inflammatory response might form the mechanistic link between low serum Mg⁺⁺ levels, larger hematoma size and greater HE. However, randomized clinical trials administering intravenous Mg⁺⁺ have shown no benefit over placebo in ICH patients. The confounding effect of hypocalcemia and a delay in Mg⁺⁺ trafficking across the blood-brain barrier might explain the futile results for intravenous Mg⁺⁺ therapy. In the current review, we will discuss the evidence regarding the possible role of low serum Mg⁺⁺ level on HE in acute ICH.

Low Serum Calcium and Magnesium Levels and Rupture of Intracranial Aneurysms

BACKGROUND AND PURPOSE

Both low serum calcium and magnesium levels have been associated with the extent of bleeding in patients with intracerebral hemorrhage, suggesting hypocalcemia- and hypomagnesemia-induced coagulopathy as a possible underlying mechanism. We hypothesized that serum albumin-corrected total calcium and magnesium levels are associated with ruptured intracranial aneurysms.

METHODS

The medical records of 4701 patients, including 1201 prospective patients, diagnosed at the Brigham and Women's Hospital and Massachusetts General Hospital between 1990 and 2016 were reviewed and analyzed. One thousand two hundred seventy-five patients had available serum calcium, magnesium, and albumin values within 1 day of diagnosis. Individuals were divided into cases with ruptured aneurysms and controls with unruptured aneurysms. Univariable and multivariable logistic regression analyses were performed to determine the association between serum albumin-corrected total calcium and magnesium levels and ruptured aneurysms.

RESULTS

In multivariable analysis, both albumin-corrected calcium (odds ratio, 0.33; 95% confidence interval, 0.27-0.40) and magnesium (odds ratio, 0.40; 95% confidence interval, 0.28-0.55) were significantly and inversely associated with ruptured intracranial aneurysms.

CONCLUSIONS

In this large case-control study, hypocalcemia and hypomagnesemia at diagnosis were significantly associated with ruptured aneurysms. Impaired hemostasis caused by hypocalcemia and hypomagnesemia may explain this association.

Serum magnesium but not calcium was associated with hemorrhagic transformation in stroke overall and stroke subtypes: a case-control study in China

Association between serum calcium and magnesium versus hemorrhagic transformation (HT) remains to be identified. A total of 1212 non-thrombolysis patients with serum calcium and magnesium collected within 24 h from stroke onset were enrolled. Backward stepwise multivariate logistic regression analysis was conducted to investigate association between calcium and magnesium versus HT. Calcium and magnesium were entered into logistic regression analysis in two models, separately: model 1, as continuous variable (per 1-mmol/L increase), and model 2, as four-categorized variable (being collapsed into quartiles). HT occurred in 140 patients (11.6%). Serum calcium was slightly lower in patients with HT than in patient without HT (P = 0.273). But serum magnesium was significantly lower in patients with HT than in patients without HT (P = 0.007). In logistic regression analysis, calcium displayed no association with HT. Magnesium, as either continuous or four-categorized variable, was independently and inversely associated with HT in stroke overall and stroke of large-artery atherosclerosis (LAA). The results demonstrated that serum calcium had no association with HT in patients without thrombolysis after acute ischemic stroke. Serum magnesium in low level was independently associated with increasing HT in stroke overall and particularly in stroke of LAA.

Serum Magnesium Levels and Outcomes in Patients With Acute Spontaneous Intracerebral Hemorrhage

BACKGROUND

Magnesium (Mg) has potential hemostatic properties. We sought to investigate the potential association of serum Mg levels (at baseline and at 48 hours) with outcomes in patients with acute spontaneous intracerebral hemorrhage (ICH).

METHODS AND RESULTS

We reviewed data on all patients with spontaneous ICH with available Mg levels at baseline, over a 5-year period. Clinical and radiological outcome measures included initial hematoma volume, admission National Institutes of Health Stroke Scale and ICH scores, in-hospital mortality, favorable functional outcome (modified Rankin Scale scores, 0-1), and functional independence (modified Rankin Scale scores, 0-2) at discharge. Our study population consisted of 299 patients with ICH (mean age, 61±13 years; mean admission serum Mg, 1.8±0.3 mg/dL). Increasing admission Mg levels strongly correlated with lower admission National Institutes of Health Stroke Scale score (Spearman's r, -0.141; P=0.015), lower ICH score (Spearman's r, -0.153; P=0.009), and lower initial hematoma volume (Spearman's r, -0.153; P=0.012). Higher admission Mg levels were documented in patients with favorable functional outcome (1.9±0.3 versus 1.8±0.3 mg/dL; P=0.025) and functional independence (1.9±0.3 versus 1.8±0.3 mg/dL; P=0.022) at discharge. No association between serum Mg levels at 48 hours and any of the outcome variables was detected. In multiple linear regression analyses, a 0.1-mg/dL increase in admission serum Mg was independently and negatively associated with the cubed root of hematoma volume at admission (regression coefficient, -0.020; 95% confidence interval, -0.040 to -0.000; P=0.049) and admission ICH score (regression coefficient, -0.053; 95% confidence interval, -0.102 to -0.005; P=0.032).

CONCLUSIONS

Higher admission Mg levels were independently related to lower admission hematoma volume and lower admission ICH score in patients with acute spontaneous ICH.

The role of the tissue factor pathway in haemostasis and beyond

PURPOSE OF REVIEW

The role of tissue factor (TF) in the initiation of the blood coagulation network leading to generation of a fibrin clot has been well defined over the past 50 years. Although much is known about this sequence of events and its regulation, many important questions remain unresolved. More recently, a complex role for TF in cellular processes independent of fibrin generation has emerged. This review summarizes some of the advances in this field.

RECENT FINDINGS

TF is the cellular receptor and cofactor for factor VII/VIIa; however, controversy still surrounds expression of TF within the vasculature, the role of circulating microvesicle pools of TF and mechanisms of 'encryption' of TF activity. However, there have been significant advances in the role of TF-initiated cell signalling. Lastly, an alternatively spliced TF transcript has been identified and some insights into its role in cancer cell metastasis/proliferation have been elucidated.

SUMMARY

Understanding of TF structure function has increased substantially; however, multiple controversies still surround some aspects of its regulation. TF has emerged as a pivotal player in orchestrating not only fibrin generation but wound repair. Derangement of these repair processes contributes significantly to the pathophysiology of a number of disease processes.

Magnesium, hemostasis, and outcomes in patients with intracerebral hemorrhage

OBJECTIVE

We tested the hypothesis that admission serum magnesium levels are associated with hematoma volume, hematoma growth, and functional outcomes in patients with intracerebral hemorrhage (ICH).

METHODS

Patients presenting with spontaneous ICH were enrolled in an observational cohort study that prospectively collected demographic, clinical, laboratory, radiographic, and outcome data. We performed univariate and adjusted multivariate analyses to assess for associations between serum magnesium levels and initial hematoma volume, final hematoma volume, and in-hospital hematoma growth as radiographic measures of hemostasis, and functional outcome measured by the modified Rankin Scale (mRS) at 3 months.

RESULTS

We included 290 patients for analysis. Admission serum magnesium was 2.0 ± 0.3 mg/dL. Lower admission magnesium levels were associated with larger initial hematoma volumes on univariate (p = 0.02), parsimoniously adjusted (p = 0.002), and fully adjusted models (p = 0.006), as well as greater hematoma growth (p = 0.004, p = 0.005, and p = 0.008, respectively) and larger final hematoma volumes (p = 0.02, p = 0.001, and p = 0.002, respectively). Lower admission magnesium level was associated with worse functional outcomes at 3 months (i.e., higher mRS; odds ratio 0.14, 95% confidence interval 0.03-0.64, p = 0.011) after adjustment for age, admission Glasgow Coma Scale score, initial hematoma volume, time from symptom onset to initial CT, and hematoma growth, with evidence that the effect of magnesium is mediated through hematoma growth.

CONCLUSIONS

These data support the hypothesis that magnesium exerts a clinically meaningful influence on hemostasis in patients with ICH.

Bio-Adaption between Magnesium Alloy Stent and the Blood Vessel: A Review

Biodegradable magnesium (Mg) alloy stents are the most promising next generation of bio-absorbable stents. In this article, we summarized the progresses on the in vitro studies, animal testing and clinical trials of biodegradable Mg alloy stents in the past decades. These exciting findings led us to propose the importance of the concept "bio-adaption" between the Mg alloy stent and the local tissue microenvironment after implantation. The healing responses of stented blood vessel can be generally described in three overlapping phases: inflammation, granulation and remodeling. The ideal bio-adaption of the Mg alloy stent, once implanted into the blood vessel, needs to be a reasonable function of the time and the space/dimension. First, a very slow degeneration of mechanical support is expected in the initial four months in order to provide sufficient mechanical support to the injured vessels. Although it is still arguable whether full mechanical support in stented lesions is mandatory during the first four months after implantation, it would certainly be a safety design parameter and a benchmark for regulatory evaluations based on the fact that there is insufficient human in vivo data available, especially the vessel wall mechanical properties during the healing/remodeling phase. Second, once the Mg alloy stent being degraded, the void space will be filled by the regenerated blood vessel tissues. The degradation of the Mg alloy stent should be 100% completed with no residues, and the degradation products (e.g., ions and hydrogen) will be helpful for the tissue reconstruction of the blood vessel. Toward this target, some future research perspectives are also discussed.

Exogenous Magnesium Chloride Reduces the Activated Partial Thromboplastin Times of Lupus Anticoagulant-Positive Patients

The activated partial thromboplastin time (APTT) assay is a basic hemostatic assay based on the time it takes for clots to form in plasma samples after the addition of calcium chloride. It is used to screen for various coagulation disorders. Several previous reports have suggested that magnesium (Mg) might contribute to coagulation reactions by binding to specific coagulation proteins. We investigated the effects of Mg on the APTT. In healthy controls, the APTT was significantly prolonged in proportion to the increase in the concentration of magnesium chloride in the range from 2.1 to 16.7 mmol/L. Among eight samples from patients with various disorders that exhibited prolonged APTT, two samples demonstrated shorter APTT when Mg was added, both of which were from patients that were positive for lupus anticoagulant. When we examined 206 clinical APTT samples, we found that Mg shortened the APTT of two samples. These two samples were also from lupus anticoagulant-positive patients (p-value: <0.003). Our findings regarding the unique effects of exogenous Mg on the APTT of lupus anticoagulant-positive patients might shed light on the role of Mg in APTT assays and lead to the development of a novel screening method for lupus anticoagulant.

Ion-Exchange Resin Anticoagulation (I-ERA): A Novel Extracorporeal Technique for Regional Anticoagulation

BACKGROUND

Extracorporeal treatments always require blood anticoagulation. We tested feasibility and efficacy of a novel technique for regional extracorporeal blood anticoagulation based on calcium removal by ion-exchange resins (i-ER), called ion-exchange resin anticoagulation (i-ERA).

METHODS

Eight swine were connected to a veno-venous extracorporeal circuit comprising a hemodiafilter and an i-ER. Blood flow was 150 mL/min. Hemodiafiltrate was generated at 975 mL/min and passed through the i-ER. A fraction of the calcium-free hemodiafiltrate was returned to the hemodiafilter (675 mL/min), while the remaining was recirculated prior the hemodiafilter (300 mL/min) to dilute blood entering the hemodiafilter. A calcium replacement solution was continuously infused. Two hours after i-ERA start, blood was sampled from inlet, before the hemodiafilter (prehemodiafilter blood) and from outlet of the extracorporeal circuit for ionized calcium (iCa) concentration and thromboelastography (TEG). Arterial blood was collected for blood gas analyses, electrolytes concentrations, and plasma free hemoglobin. Hemodynamics and ventilation were monitored.

RESULTS

i-ERA reduced iCa from 1.28 ± 0.05 mmol/L (inlet) to 0.47 ± 0.03 mmol/L (prehemodiafilter blood) and 0.25 ± 0.03 mmol/L (outlet). Prehemodiafilter blood and outlet samples showed no sign of clot formation (reaction time (R) >60 min; maximal amplitude (MA) = 0 (0-0) mm), while blood-inlet had normal coagulation (R = 8.5 (5.8-10.2) min; MA = 65.2 (63.2-68.7) mm). Arterial gas analyses and electrolytes concentrations, hemodynamics, and ventilation were unchanged. No hemolysis was recorded.

CONCLUSIONS

In a swine model, i-ERA proved feasible and effective in reducing iCa and preventing clot formation with TEG analyses. Further studies are warranted to evaluate the long-term efficacy and safety of i-ERA.

LEVEL OF EVIDENCE

V-therapeutic animal experiment.

Structure-Function Relationship of the Interaction between Tissue Factor and Factor VIIa

Interactions between tissue factor and factor VIIa are the primary initiators of coagulation in hemostasis and certain thrombotic diseases. Tissue factor, an integral membrane protein expressed extensively outside of the vasculature, is the regulatory protein cofactor for coagulation factor VIIa. Factor VIIa, a trypsin-like serine protease homologous with other blood coagulation proteases, is weakly active when free in solution and must bind its membrane-bound cofactor for physiologically relevant activity. Tissue factor allosterically activates factor VIIa by several mechanisms such as active site positioning, spatial stabilization, and direct interactions with the substrate. Protein-membrane interactions between tissue factor, factor VIIa, and substrates all play critical roles in modulating the activity of this enzyme complex. Additionally, divalent cations such as Ca(2+) and Mg(2+) are critical for correct protein folding, as well as protein-membrane and protein-protein interactions. The contributions of these factors toward tissue factor-factor VIIa activity are discussed in this review.

Tissue Factor Residues That Modulate Magnesium-Dependent Rate Enhancements of the Tissue Factor/Factor VIIa Complex

The blood coagulation cascade is initiated when the cell-surface complex of factor VIIa (FVIIa, a trypsin-like serine protease) and tissue factor (TF, an integral membrane protein) proteolytically activates factor X (FX). Both FVIIa and FX bind to membranes via their γ-carboxyglutamate-rich domains (GLA domains). GLA domains contain seven to nine bound Ca(2+) ions that are critical for their folding and function, and most biochemical studies of blood clotting have employed supraphysiologic Ca(2+) concentrations to ensure saturation of these domains with bound Ca(2+). Recently, it has become clear that, at plasma concentrations of metal ions, Mg(2+) actually occupies two or three of the divalent metal ion-binding sites in GLA domains, and that these bound Mg(2+) ions are required for full function of these clotting proteins. In this study, we investigated how Mg(2+) influences FVIIa enzymatic activity. We found that the presence of TF was required for Mg(2+) to enhance the rate of FX activation by FVIIa, and we used alanine-scanning mutagenesis to identify TF residues important for mediating this response to Mg(2+). Several TF mutations, including those at residues G164, K166, and Y185, blunted the ability of Mg(2+) to enhance the activity of the TF/FVIIa complex. Our results suggest that these TF residues interact with the GLA domain of FX in a Mg(2+)-dependent manner (although effects of Mg(2+) on the FVIIa GLA domain cannot be ruled out). Notably, these TF residues are located within or immediately adjacent to the putative substrate-binding exosite of TF.

The influence of drugs used in cardiac anaesthesia and critical care on multiple electrode aggregometry: an in-vitro volunteer study

BACKGROUND

Multiple electrode aggregometry (MEA) is a point-of-care test evaluating platelet function and the efficacy of platelet inhibitors. In MEA, electrical impedance of whole blood is measured after addition of a platelet activator. Reduced impedance implies platelet dysfunction or the presence of platelet inhibitors. MEA plays an increasingly important role in the management of perioperative platelet dysfunction. In vitro, midazolam, propofol, lidocaine and magnesium have known antiplatelet effects and these may interfere with MEA interpretation.

OBJECTIVE

To evaluate the extent to which MEA is modified in the presence of these drugs.

DESIGN

An in-vitro study using blood collected from healthy volunteers.

SETTING

Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland, 2010 to 2011.

PATIENTS

Twenty healthy volunteers.

INTERVENTION

Measurement of baseline MEA was using four activators: arachidonic acid, ADP, TRAP-6 and collagen. The study drugs were then added in three increasing, clinically relevant concentrations.

MAIN OUTCOME MEASURE

MEA was compared with baseline for each study drug.

RESULTS

Midazolam, propofol and lidocaine showed no effect on MEA at any concentration. Magnesium at 2.5 mmol l had a significant effect on the ADP and TRAP tests (31 ± 13 and 96 ± 39 AU, versus 73 ± 21 and 133 ± 28 AU at baseline, respectively), and a less pronounced effect at 1 mmol l on the ADP test (39 ± 0 AU).

CONCLUSION

Midazolam, propofol and lidocaine do not interfere with MEA measurement. In patients treated with high to normal doses of magnesium, MEA results for ADP and TRAP-tests should be interpreted with caution.

TRIAL REGISTRATION

Clinicaltrials.gov (no. NCT01454427).

Functional significance of calcium binding to tissue-nonspecific alkaline phosphatase

The conserved active site of alkaline phosphatases (AP) contains catalytically important Zn²⁺ (M1 and M2) and Mg²⁺-sites (M3) and a fourth peripheral Ca²⁺ site (M4) of unknown significance. We have studied Ca²⁺ binding to M1-4 of tissue-nonspecific AP (TNAP), an enzyme crucial for skeletal mineralization, using recombinant TNAP and a series of M4 mutants. Ca²⁺ could substitute for Mg²⁺ at M3, with maximal activity for Ca²⁺/Zn²⁺-TNAP around 40% that of Mg²⁺/Zn²⁺-TNAP at pH 9.8 and 7.4. At pH 7.4, allosteric TNAP-activation at M3 by Ca²⁺ occurred faster than by Mg²⁺. Several TNAP M4 mutations eradicated TNAP activity, while others mildly influenced the affinity of Ca²⁺ and Mg²⁺ for M3 similarly, excluding a catalytic role for Ca²⁺ in the TNAP M4 site. At pH 9.8, Ca²⁺ competed with soluble Zn²⁺ for binding to M1 and M2 up to 1 mM and at higher concentrations, it even displaced M1- and M2-bound Zn²⁺, forming Ca²⁺/Ca²⁺-TNAP with a catalytic activity only 4–6% that of Mg²⁺/Zn²⁺-TNAP. At pH 7.4, competition with Zn²⁺ and its displacement from M1 and M2 required >10-fold higher Ca²⁺ concentrations, to generate weakly active Ca²⁺/Ca²⁺-TNAP. Thus, in a Ca²⁺-rich environment, such as during skeletal mineralization at pH 7.4, Ca²⁺ adequately activates Zn²⁺-TNAP at M3, but very high Ca²⁺ concentrations compete with available Zn²⁺ for binding to M1 and M2 and ultimately displace Zn²⁺ from the active site, virtually inactivating TNAP. Those ALPL mutations that substitute critical TNAP amino acids involved in coordinating Ca²⁺ to M4 cause hypophosphatasia because of their 3D-structural impact, but M4-bound Ca²⁺ is catalytically inactive. In conclusion, during skeletal mineralization, the building Ca²⁺ gradient first activates TNAP, but gradually inactivates it at high Ca²⁺ concentrations, toward completion of mineralization.

Ca2+ switches the effect of PS-containing membranes on Factor Xa from activating to inhibiting: implications for initiation of blood coagulation

Calcium (Ca2+) plays a pivotal role in cellular and organismal physiology. The Ca2+ ion has an intermediate protein-binding affinity and thus it can serve as an on/off switch in the regulation of different biochemical processes. The serum level of ionized Ca2+ is regulated with normal ionized Ca2+ being in the range 1.10-1.3 mM. Hypocalcaemia (free Ca2+<1.1 mM) in critically ill patients is commonly accompanied by haemostatic abnormalities, ranging from isolated thrombocytopenia to complex defects such as disseminated intravascular coagulation, commonly thought to be due to insufficient functioning of anticoagulation pathways. A small amount of fXa (Factor Xa) produced by Factor VIIa and exposed tissue factor is key to initiating blood coagulation by producing enough thrombin to induce the later stages of coagulation. fXa must bind to PS (phosphatidylserine)-containing membranes to produce thrombin at a physiologically significant rate. In the present study, we show that overall fXa activity on PS-containing membranes is sharply regulated by a 'Ca2+ switch' centred at 1.16 mM, below which fXa is active and above which fXa forms inactive dimers on PS-exposing membranes. Our data lead to a mathematical model that predicts the variation of fXa activity as a function of both Ca2+ and membrane concentrations. Because the critical Ca2+ concentration is at the lower end of the normal plasma ionized Ca2+ concentration range, we propose a new regulatory mechanism by which local Ca2+ concentration switches fXa from an intrinsically active form to a form requiring its cofactor [fVa (Factor Va)] to achieve significant activity.

Factor VIII assay mimicking in vivo coagulation conditions

Under certain circumstances, the determination of coagulation factor VIII (FVIII) is hampered by assay discrepancies between clotting and chromogenic approaches. These are observed in certain patients' plasma as well as in certain concentrates. We intended to develop a novel assay for the quantification of coagulation FVIII which reflects the physiological situation better than the established assays. It is based on plasma without chelation of divalent cations and simultaneously minimizes the generation of activated factors which could function as uncontrolled triggers of coagulation. FVIII deficient plasma is prepared with the aid of biotinylated antibodies against FVIII from normal plasma in presence of inhibitors of contact activation. To start the assay only tiny amounts of activated FIX serve as trigger. The FVIII determination is performed in a kinetic experiment and is based on the cleavage of a fluorogenic substrate for activated FX. FVIII concentrations between 0.01 and 1 IU mL(-1) are easily determined. Plasma-derived and recombinant FVIII concentrates were compared. All plasma-derived concentrates were found to contain FVIII activities within the specification of the manufacturer. Recombinant concentrates yielded only 35-50% of the claimed potency. The novel in vivo-like assay avoids the undue advantage or disadvantage of certain product characteristics by eliminating unphysiological assay conditions. Its usefulness could turn out in future experiments with plasma from haemophilia A patients.

Structural and functional studies of γ-carboxyglutamic acid domains of factor VIIa and activated Protein C: role of magnesium at physiological calcium

Crystal structures of factor (F) VIIa/soluble tissue factor (TF), obtained under high Mg(2+) (50mM Mg(2+)/5mM Ca(2+)), have three of seven Ca(2+) sites in the γ-carboxyglutamic acid (Gla) domain replaced by Mg(2+) at positions 1, 4, and 7. We now report structures under low Mg(2+) (2.5mM Mg(2+)/5mM Ca(2+)) as well as under high Ca(2+) (5mM Mg(2+)/45 mM Ca(2+)). Under low Mg(2+), four Ca(2+) and three Mg(2+) occupy the same positions as in high-Mg(2+) structures. Conversely, under low Mg(2+), reexamination of the structure of Gla domain of activated Protein C (APC) complexed with soluble endothelial Protein C receptor (sEPCR) has position 4 occupied by Ca(2+) and positions 1 and 7 by Mg(2+). Nonetheless, in direct binding experiments, Mg(2+) replaced three Ca(2+) sites in the unliganded Protein C or APC. Further, the high-Ca(2+) condition was necessary to replace Mg4 in the FVIIa/soluble TF structure. In biological studies, Mg(2+) enhanced phospholipid binding to FVIIa and APC at physiological Ca(2+). Additionally, Mg(2+) potentiated phospholipid-dependent activations of FIX and FX by FVIIa/TF and inactivation of activated factor V by APC. Since APC and FVIIa bind to sEPCR involving similar interactions, we conclude that under the low-Mg(2+) condition, sEPCR binding to APC-Gla (or FVIIa-Gla) replaces Mg4 by Ca4 with an attendant conformational change in the Gla domain ω-loop. Moreover, since phospholipid and sEPCR bind to FVIIa or APC via the ω-loop, we predict that phospholipid binding also induces the functional Ca4 conformation in this loop. Cumulatively, the data illustrate that Mg(2+) and Ca(2+) act in concert to promote coagulation and anticoagulation.

Non-enzymatic proteins from snake venoms: a gold mine of pharmacological tools and drug leads

Non-enzymatic proteins from snake venoms play important roles in the immobilization of prey, and include some large and well-recognized families of toxins. The study of such proteins has expanded not only our understanding of venom toxicity, but also the knowledge of normal and disease states in human physiology. In many cases their characterization has led to the development of powerful research tools, diagnostic techniques, and pharmaceutical drugs. They have further yielded basic understanding of protein structure-function relationships. Therefore a number of studies on these non-enzymatic proteins had major impact on several life science and medical fields. They have led to life-saving therapeutics, the Nobel prize, and development of molecular scalpels for elucidation of ion channel function, vasoconstriction, complement system activity, platelet aggregation, blood coagulation, signal transduction, and blood pressure regulation. Here, we identify research papers that have had significant impact on the life sciences. We discuss how these findings have changed the course of science, and have also included the personal recollections of the original authors of these studies. We expect that this review will provide impetus for even further exciting research on novel toxins yet to be discovered.

The effects of magnesium on the course of atrial fibrillation and coagulation in patients with atrial fibrillation undergoing mitral valve annuloplasty

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Magnesium has been reported to be effective in reducing the incidence or prophylaxis of AF. Magnesium is also an essential constituent of many enzyme systems and plays a physiological role in coagulation regulation. The aim of the present study was to examine the effects of magnesium, whether magnesium infusion might decrease the incidence of AF and induce hypocoagulable state in patients with AF, who were undergoing mitral valve annuloplasty.

Methods

This prospective laboratory study was performed using blood from patients with AF undergoing mitral valve annuloplasty. The radial artery was punctured with a 20 gauge catheter and used for monitoring continuous arterial pressure and blood sampling. After anesthesia induction, 4 g of magnesium was mixed with 100 ml normal saline and infused for 5 minutes. Magnesium, calcium, activated clotting time (ACT) and thromboelastographic parameters were checked before and 60 minutes after the magnesium infusion. The electrocardiography changes after magnesium infusion were also checked before commencing cardiopulmonary bypass.

Results

After magnesium infusion, the serum level of magnesium increased significantly but serum calcium did not change significantly. ACT did not change significantly before or after magnesium infusion. The thromboelastographic parameters showed no significant changes before or after magnesium infusion. None of the patients converted to sinus rhythm from AF after the magnesium infusion.

Conclusions

A magnesium infusion did not influence the course of AF and coagulation in patients during prebypass period with AF undergoing mitral valve annuloplasty.

Nutritional deficiencies and phospholipid metabolism

Phospholipids are important components of the cell membranes of all living species. They contribute to the physicochemical properties of the membrane and thus influence the conformation and function of membrane-bound proteins, such as receptors, ion channels, and transporters and also influence cell function by serving as precursors for prostaglandins and other signaling molecules and modulating gene expression through the transcription activation. The components of the diet are determinant for cell functionality. In this review, the effects of macro and micronutrients deficiency on the quality, quantity and metabolism of different phospholipids and their distribution in cells of different organs is presented. Alterations in the amount of both saturated and polyunsaturated fatty acids, vitamins A, E and folate, and other micronutrients, such as zinc and magnesium, are discussed. In all cases we observe alterations in the pattern of phospholipids, the more affected ones being phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. The deficiency of certain nutrients, such as essential fatty acids, fat-soluble vitamins and some metals may contribute to a variety of diseases that can be irreversible even after replacement with normal amount of the nutrients. Usually, the sequelae are more important when the deficiency is present at an early age.

Risk factors and outcome associated with hypomagnesemia in massive transfusion

BACKGROUND

Electrolyte disturbances are common in patients with critical bleeding requiring massive transfusion. The risk factors and outcome associated with the occurrence of hypomagnesemia in massive transfusion remain uncertain.

STUDY DESIGN AND METHODS

A cohort of 353 consecutive patients who required massive transfusion, defined as 10 or more units of allogeneic red blood cells or whole blood transfusion within 24 hours, between 2002 and 2008 in a quaternary health care center in Western Australia was considered. Logistic regression was used to identify risk factors and outcome associated with hypomagnesemia during massive transfusion (<0.7 mmol/L or 1.7 mg/dL).

RESULTS

Of the 353 patients requiring massive transfusion during the study period, 298 patients (84%) had serum magnesium concentrations available for analysis. Hypomagnesemia was common (172 patients, 58%), and the mean magnesium concentration was 0.68 mmol/L (1.65 mg/dL; standard deviation, 0.15 mmol/L) in these patients. The risk factors for hypomagnesemia were hypocalcemia (odds ratio [OR], 1.67 per 0.1 mmol/L decrement; 95% confidence interval [CI], 1.36-2.01; p = 0.001) and hypofibrinogenemia (OR, 1.05 per 0.1 g/L decrement; 95% CI, 1.01-1.09; p = 0.009). The lowest serum magnesium concentrations were associated with the lowest ionized calcium concentrations (Spearman correlation coefficient, 0.377; p = 0.001). Both magnesium concentrations (OR, 0.91 per 0.1 mmol/L increment; 95% CI 0.31-2.69; p = 0.863) and the interaction term between magnesium and calcium concentrations were not associated with an increased risk of mortality after adjusting for other covariates.

CONCLUSIONS

Hypomagnesemia was common and associated with hypocalcemia in massive transfusion, but serum magnesium concentrations had no independent effect or interactive effect with hypocalcemia on mortality of patients requiring massive transfusion.