Abnormal von Willebrand factor secretion, factor VIII stabilization and thrombus dynamics in type 2N von Willebrand disease mice.

Essentials Type 2N von Willebrand disease involves impaired von Willebrand factor to factor VIII binding. Type 2N von Willebrand disease mutations exhibit qualitative and mild quantitative deficiencies. Type 2N von Willebrand disease mice exhibit unstable venous hemostatic thrombi. The factor VIII-binding ability of von Willebrand factor regulates arteriole thrombosis dynamics. SUMMARY: Background von Willebrand factor (VWF) and factor VIII (FVIII) circulate as a non-covalent complex, with VWF serving as the carrier for FVIII. VWF indirectly influences secondary hemostasis by stabilizing FVIII and transporting it to the site of primary hemostasis. Type 2N von Willebrand disease involves impaired binding of VWF to FVIII, resulting in decreased plasma levels of FVIII. Objectives In these studies, we characterize the impact of three type 2N VWD variants (R763A, R854Q, R816W) on VWF secretion, FVIII stabilization and thrombus formation in a murine model. Methods Type 2N VWD mice were generated by hydrodynamic injections of mutant murine VWF cDNAs and the influence of these variants on VWF secretion and FVIII binding was evaluated. In vivo hemostasis and the dynamics of thrombus formation and embolization were assessed using a murine tail vein transection hemostasis model and an intravital thrombosis model in the cremaster arterioles. Results Type 2N VWD variants were associated with decreased VWF secretion using cell and animal-based models. FVIII-binding to type 2N variants was impaired in vitro and was variably stabilized in vivo by expressed or infused 2N variant VWF protein. Both transgenic type 2N VWD and FVIII knockout (KO) mice demonstrated impaired thrombus formation associated with decreased thrombus stability. Conclusions The type 2N VWD phenotype can be recapitulated in a murine model and is associated with both quantitative and qualitative VWF deficiencies and impaired thrombus formation. Patients with type 2N VWD may have normal primary hemostasis formation but decreased thrombus stability related to ineffective secondary hemostasis.

Histones link inflammation and thrombosis through the induction of Weibel-Palade body exocytosis.

Essentials Dysregulated DNA and histone release can promote pathological immunothrombosis. Weibel-Palade bodies (WPBs) are sentinel-like organelles that respond to proinflammatory stimuli. Histones induce WPB exocytosis in a caspase, calcium and charge-dependent mechanism. A targetable axis may exist between DNA/histones and WPBs in inflammation and immunothrombosis. SUMMARY: Background Damage-associated molecular patterns (DAMPs), including molecules such as DNA and histones, are released into the blood following cell death. DAMPs promote a procoagulant phenotype through enhancement of thrombin generation and platelet activation, thereby contributing to immunothrombosis. Weibel-Palade bodies (WPBs) are dynamic endothelial cell organelles that contain procoagulant and proinflammatory mediators, such as von Willebrand factor (VWF), and are released in response to cell stresses. VWF mediates platelet adhesion and aggregation, and has been implicated as a procoagulant component of the innate immune response. Objective To determine the influence of histones and DNA on WPB release, and characterize their association in models of inflammation. Methods We treated C57BL/6J mice and cultured endothelial cells with histones (unfractionated, lysine-rich or arginine-rich) and DNA, and measured WPB exocytosis. We used inhibitors to determine a mechanism of histone-induced WPB release in vitro. We characterized the release of DAMPs and WPBs in response to acute and chronic inflammation in human and murine models. Results and conclusions Histones, but not DNA, induced the release of VWF (1.46-fold) from WBPs and caused thrombocytopenia (0.74-fold), which impaired arterial thrombus formation in mice. Histones induced WPB release from endothelial cells in a caspase-dependent, calcium-dependent and charge-dependent manner, and promoted platelet capture in a flow chamber model of VWF-platelet string formation. The levels of DAMPs and WPB-released proteins were elevated during inflammation, and were positively correlated in chronic inflammation. These studies showed that DAMPs can regulate the function and level of VWF by inducing its release from endothelial WPBs. This DAMP-WPB axis may propagate immunothrombosis associated with inflammation.

The laryngeal mask airway: a new standard for airway evaluation in thoracic surgery.

BACKGROUND: Thoracic surgeons typically perform fiberoptic bronchoscopy (FOB) before thoracotomy, usually on the day of the operation after intubation with a single-lumen endotracheal tube (ETT) and before insertion of a double-lumen ETT. This routine requires two laryngoscopies and two intubations. The laryngeal mask airway (LMA) is an airway device developed in England and approved by the Food and Drug Administration in 1991 for clinical use in the United States. It requires neither mask ventilation nor laryngoscopy and allows FOB visualization of the epiglottis, larynx, and entire trachea. We assessed the LMA as an alternative to a single-lumen ETT for FOB before thoracotomy. METHODS: Through prospective assessment, 50 patients underwent FOB after insertion of an LMA before thoracotomy. Pulse rate, blood pressure, ease of insertion of the LMA, quality of FOB, and complications of LMA insertion were assessed. RESULTS: During LMA insertion, blood pressure and pulse rate increased less than 5% from baseline in all patients. The LMA was inserted successfully in all patients within 10 seconds. No complications occurred as a result of LMA insertion. CONCLUSIONS: Insertion of the LMA causes minimal hemodynamic response. From the time of induction of general anesthesia, insertion of the LMA is quick, simple, and safe and eliminates the need for endotracheal intubation with a single-lumen ETT before double-lumen tube insertion. The LMA, in contrast to the ETT, allows a complete survey of the larynx and trachea. The LMA is autoclavable, reusable, and cost effective. Therefore, in patients who require FOB immediately before thoracotomy, LMA use should be the standard for airway evaluation.

Edge detection at multiple locations using a 'radar' tracking algorithm as exemplified in isolated guinea-pig lymphatic vessels.

An algorithm based on the Kalman filter and used for tracking a target in a noisy environment has been applied to monitoring the position of moving boundaries as recorded by a video camera. The method, termed the Probabilistic Data Association Filter, is computationally efficient, allowing simultaneous monitoring at many positions along the boundary at video frame rates of 25 Hz. The present study uses the tracking procedure to investigate and correlate constrictions along lymphatic vessels. The procedure is well suited for real time tracking of visualised biological events including the simultaneous monitoring of constrictions in networks of blood vessels, the movement of cells or the trajectory of intracellular events monitored by intracellular fluorescent markers.

Participation of alpha 2-adrenergic receptors in neural vascular tone of canine skeletal muscle.

Studies were carried out in anesthetized, paralyzed, and ventilated dogs to determine whether postsynaptic alpha 2-adrenergic receptors participated in neurally mediated vascular tone in skeletal muscle. Hindlimb skeletal muscle resistance (RL) and blood flow (QL) were determined before, during, and after reversible cold block of the sciatic nerve. This sequence of observations was repeated 30 min after blockade of alpha 1-adrenergic receptors with prazosin. Then the alpha 2-adrenergic receptors were blocked with yohimbine, and the nerve cold block was repeated. When the sciatic nerve was cold blocked before alpha 1-adrenergic blockade, RL decreased approximately 50% and QL increased 75% (P less than 0.05) and then returned to control when the nerve was rewarmed. After alpha 1-block 76% of neural tone remained as assessed by nerve cooling (P less than 0.05). This phenomenon occurred despite effective alpha 1-adrenergic blockade as assessed by the alpha 1-receptor agonist methoxamine. With alpha 1- plus alpha 2-block no change in RL or QL was seen with nerve cold block. The same protocol was repeated in a second series of animals, but mean arterial pressure, which fell after alpha 1-block in the group above, was maintained by dextran infusion at normotensive levels. In these animals, 40% of neural tone remained after alpha 1-block. Both alpha 1- and alpha 2-adrenergic blockers were again needed to abolish the QL and RL response to nerve cold block. In another series of animals, yohimbine was administered before prazosin. In this series, alpha 2-adrenergic blockade greatly reduced neural tone as assessed by nerve cooling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenoceptor regulation of canine skeletal muscle blood flow during carbon monoxide hypoxia.

We questioned whether carbon monoxide hypoxia (COH) would affect peripheral blood flow by neural activation of adrenoceptors to the extent we had found in other forms of hypoxia. We studied this problem in hindlimb muscles of four groups of anesthetized dogs (untreated, alpha 1-blocked, alpha 1 + alpha 2-blocked, and beta 2-blocked). Cardiac output increased, but hindlimb blood flow (QL) and resistance (RL) remained at prehypoxic levels during COH (O2 content reduced 50%) in untreated animals. When activity in the sciatic nerve was reversibly cold blocked, QL doubled and RL decreased 50%. These changes with nerve block were the same during COH, suggesting that neural activity to hindlimb vasculature was not increased by COH. In animals treated with phenoxybenzamine (primarily alpha 1-blocked), RL dropped (approximately 50%) during COH, an indication that catecholamines played a significant role in maintaining tone to skeletal muscle. Animals with both alpha 1 + alpha 2-adrenergic blockade (phenoxybenzamine and yohimbine added) did not survive COH. RL was higher in beta 2-block than in the untreated group during COH, but nerve cooling indicated that beta 2-adrenoceptor vasodilation was accomplished primarily by humoral means. The above findings demonstrated that adrenergic receptors were important in the regulation of QL and RL during COH, but they were not activated by sympathetic nerve stimulation to the limb muscles.

First pass uptake of 14C-propranolol by the lung.

Uptake of 14C-propranolol by the lungs during a single passage through the pulmonary circulation was measured in ten patients at cardiac catheterisation. Mean lung uptake of propranolol was 75% in seven patients who were not previously taking the drug and 33% in three patients who were taking it as regular oral treatment. Lung uptake of propranolol in man is therefore considerable and is partly saturable by normal oral doses. This may alter the dose response relation for propranolol and a wide range of other drugs when given intravenously. The method used to study lung uptake is simple and might be suitable for studies of endothelial cell function in disease.

Giant sertoli cell adenoma in testicular feminization syndrome.

An extremely large Sertoli cell adenoma discovered incidentally in an elderly phenotypically femal patient with testicular feminization syndrome is reported. The patient is alive 3 years following removal of the tumor.

Primitive neuroectodermal tumor (neuroblastoma) arising in sciatic nerve of a child.

A well-documented case of a primitive neuroectodermal tumor (neuroblastoma) arising in the sciatic nerve of a 6-year old boy is presented. After radical surgical excision of the tumor, followed by chemotherapy, the child remained clinically free of disease for 20 months. Tumor then recurred locally followed by widespread dissemination. He expired 2 years postoperatively. The literature on this type of rare and controversial tumor of peripheral nerves is reviewed. Only a very few reported cases are considered fully acceptable. Interest in this subject, and adequate documentation of future reported cases may lead to a better understanding of this class of malignant tumors.