Conditions controlling tumor cytotoxicity of rat liver macrophages mediated by liposomal muramyl dipeptide

Activation of rat liver macrophages with free and liposome-encapsulated muramyl dipeptide (MDP) to a tumorcytotoxic state was characterized by employing various experimental conditions. Macrophage-mediated tumor cytotoxicity was determined using two standard assay systems: a[methyl]-3H]thymidine release assay to measure the extent of tumor cell lysis and a[methyl-3H]thymidine incorporation assay to measure the combined effects of tumor cell lysis and stasis. The extent of cell lysis was not affected by the ratio of macrophages to tumor cells within the ratio range of 30:1 to 5:1, provided that the macrophages form a confluent monolayer. Tumor cell lysis, however, was significantly influenced by macrophage density; a low macrophage density for example resulted in a low percentage of tumor cell lysis. Tumor target cells used in this study, i.e., C26 adenocarcinoma, B16 melanoma and P815 mastocytoma, differed in their susceptibility towards macrophage-mediated cell lysis, whereas no differences were observed with respect to tumor cell stasis. Non-tumorigenic cell lines such as human fibroblastic cells and LLC monkey kidney cells were not lysed by activated macrophages, although proliferation of these cells was markedly inhibited. Additionally, the effects of liposomal lipid composition on macrophage activation were studied. With a basic composition of phospholipid/cholesterol/dicetylphosphate, we used either egg-yolk, dipalmitoyl-, distearoyl- or dihexadecylphosphatidylcholine as the bulk phospholipid constituent. Although these liposomes display a widely different susceptibility to lysosomal phospholipase activities, we could not detect any significant difference in either the extent or the duration of the tumoricidal activity induced by MDP encapsulated in these different types of liposome

Effect of cholesterol on the uptake and intracellular degradation of liposomes by liver and spleen:A combined biochemical and γ-ray perturbed angular correlation study

We investigated the effect of cholesterol on the uptake and intracellular degradation of liposomes by rat liver and spleen macrophages. Multilamellar vesicles (MLV) consisting of distearoylphosphatidylcholine/phosphatidylserine (molar ratio 9:1) or distearoylphosphatidylcholine/cholesterol/phosphatidylserine (molar ratio 4:5:1) were labeled with [3H]cholesteryl hexadecyl ether and/or cholesteryl [14C]oleate. After i.v. injection the cholesterol-containing liposomes were eliminated less rapidly from the bloodstream and taken up to a lesser extent by the liver (macrophages) than the cholesterol-free liposomes. Assessment of the 3H/14C ratios in liver and spleen cells revealed that the cholesterol-containing liposomes are substantially more resistant towards intracellular degradation than the cholesterol-free liposomes. These results could be confirmed by measuring the release of 111In from liposomes after uptake by liver and spleen by means of γ-ray perturbed angular correlation spectroscopy. Experiments with cultured Kupffer cells in monolayer also revealed that incorporation of cholesterol results in a decrease of the uptake and an increase of the intracellular stability of cholesteryl [14C]oleate-labeled liposomes. Finally, incubation of both types of liposomes with lysosomal fractions prepared from rat liver demonstrated a difference in susceptibility to lysosomal degradation: the cholesterol-free vesicles were much more sensitive to lysosomal esterase than the cholesterol-containing liposomes. These results may be relevant to the application of liposomes as a drug carrier system to liver and spleen (macrophages

Antithrombotic management of patients with atrial fibrillation-Dutch anticoagulant initiatives anno 2020

In recent years, as more and more experience has been gained with prescribing direct oral anticoagulants (DOACs), new research initiatives have emerged in the Netherlands to improve the safety and appropriateness of DOAC treatment for stroke prevention in patients with atrial fibrillation (AF). These initiatives address several contemporary unresolved issues, such as inappropriate dosing, non-adherence and the long-term management of DOAC treatment. Dutch initiatives have also contributed to the development and improvement of risk prediction models. Although fewer bleeding complications (notably intracranial bleeding) are in general seen with DOACs in comparison with vitamin K antagonists, to successfully identify patients with high bleeding risk and to tailor anticoagulant treatment accordingly to mitigate this increased bleeding risk, is one of the research aims of recent and future years. This review highlights contributions from the Netherlands that aim to address these unresolved issues regarding the anticoagulant management in AF in daily practice, and provides a narrative overview of contemporary stroke and bleeding risk assessment strategies.Thrombosis and Hemostasi

External validation and updating of prediction models of bleeding risk in patients with cancer receiving anticoagulants.

OBJECTIVE: Patients with cancer are at increased bleeding risk, and anticoagulants increase this risk even more. Yet, validated bleeding risk models for prediction of bleeding risk in patients with cancer are lacking. The aim of this study is to predict bleeding risk in anticoagulated patients with cancer. METHODS: We performed a study using the routine healthcare database of the Julius General Practitioners' Network. Five bleeding risk models were selected for external validation. Patients with a new cancer episode during anticoagulant treatment or those initiating anticoagulation during active cancer were included. The outcome was the composite of major bleeding and clinically relevant non-major (CRNM) bleeding. Next, we internally validated an updated bleeding risk model accounting for the competing risk of death. RESULTS: The validation cohort consisted of 1304 patients with cancer, mean age 74.0±10.9 years, 52.2% males. In total 215 (16.5%) patients developed a first major or CRNM bleeding during a mean follow-up of 1.5 years (incidence rate; 11.0 per 100 person-years (95% CI 9.6 to 12.5)). The c-statistics of all selected bleeding risk models were low, around 0.56. Internal validation of an updated model accounting for death as competing risk showed a slightly improved c-statistic of 0.61 (95% CI 0.54 to 0.70). On updating, only age and a history of bleeding appeared to contribute to the prediction of bleeding risk. CONCLUSIONS: Existing bleeding risk models cannot accurately differentiate bleeding risk between patients. Future studies may use our updated model as a starting point for further development of bleeding risk models in patients with cancer

Fast, Quality, Segmentation of Large Volumes -- Isoperimetric Distance Trees

For many medical segmentation tasks, the contrast along most of the boundary of the target object is high, allowing simple thresholding or region growing approaches to provide nearly sufficient solutions for the task. However, the regions recovered by these techniques frequently leak through bottlenecks in which the contrast is low or nonexistent. We propose a new approach based on a novel speed-up of the isoperimetric algorithm [1] that can solve the problem of leaks through a bottleneck. The speed enhancement converts the isoperimetric segmentation algorithm to a fast, linear-time computation by using a tree representation as the underlying graph instead of a standard lattice structure. In this paper, we show how to create an appropriate tree substrate for the segmentation problem and how to use this structure to perform a lineartime computation of the isoperimetric algorithm. This approach is shown to overcome common problems with watershed-based techniques and to provide fast, high-quality results on large datasets

Design and rationale of DUTCH-AF: a prospective nationwide registry programme and observational study on long-term oral antithrombotic treatment in patients with atrial fibrillation

Introduction Anticoagulation therapy is pivotal in the management of stroke prevention in atrial fibrillation (AF). Prospective registries, containing longitudinal data are lacking with detailed information on anticoagulant therapy, treatment adherence and AF-related adverse events in practice-based patient cohorts, in particular for non-vitamin K oral anticoagulants (NOAC). With the creation of DUTCH-AF, a nationwide longitudinal AF registry, we aim to provide clinical data and answer questions on the (anticoagulant) management over time and of the clinical course of patients with newly diagnosed AF in routine clinical care. Within DUTCH-AF, our current aim is to assess the effect of non-adherence and non-persistence of anticoagulation therapy on clinical adverse events (eg, bleeding and stroke), to determine predictors for such inadequate anticoagulant treatment, and to validate and refine bleeding prediction models. With DUTCH-AF, we provide the basis for a continuing nationwide AF registry, which will facilitate subsequent research, including future registry-based clinical trials.Methods and analysis The DUTCH-AF registry is a nationwide, prospective registry of patients with newly diagnosed 'non-valvular' AF. Patients will be enrolled from primary, secondary and tertiary care practices across the Netherlands. A target of 6000 patients for this initial cohort will be followed for at least 2 years. Data on thromboembolic and bleeding events, changes in antithrombotic therapy and hospital admissions will be registered. Pharmacy-dispensing data will be obtained to calculate parameters of adherence and persistence to anticoagulant treatment, which will be linked to AF-related outcomes such as ischaemic stroke and major bleeding. In a subset of patients, anticoagulation adherence and beliefs about drugs will be assessed by questionnaire.Ethics and dissemination This study protocol was approved as exempt for formal review according to Dutch law by the Medical Ethics Committee of the Leiden University Medical Centre, Leiden, the Netherlands. Results will be disseminated by publications in peer-reviewed journals and presentations at scientific congresses.Cardiolog

HUMeral shaft fractures: measuring recovery after operative versus non-operative treatment (HUMMER): a multicenter comparative observational study

BACKGROUND: Fractures of the humeral shaft are associated with a profound temporary (and in the elderly sometimes even permanent) impairment of independence and quality of life. These fractures can be treated operatively or non-operatively, but the optimal tailored treatment is an unresolved problem. As no high-quality comparative randomized or observational studies are available, a recent Cochrane review concluded there is no evidence of sufficient scientific quality available to inform the decision to operate or not. Since randomized controlled trials for this injury have shown feasibility issues, this study is designed to provide the best achievable evidence to answer this unresolved problem. The primary aim of this study is to evaluate functional recovery after operative versus non-operative treatment in adult patients who sustained a humeral shaft fracture. Secondary aims include the effect of treatment on pain, complications, generic health-related quality of life, time to resumption of activities of daily living and work, and cost-effectiveness. The main hypothesis is that operative treatment will result in faster recovery. METHODS/DESIGN: The design of the study will be a multicenter prospective observational study of 400 patients who have sustained a humeral shaft fracture, AO type 12A or 12B. Treatment decision (i.e., operative or non-operative) will be left to the discretion of the treating surgeon. Critical elements of treatment will be registered and outcome will be monitored at regular intervals over the subsequent 12 months. The primary outcome measure is the Disabilities of the Arm, Shoulder, and Hand score. Secondary outcome measures are the Constant score, pain level at both sides, range of motion of the elbow and shoulder joint at both sides, radiographic healing, rate of complications and (secondary) interventions, health-related quality of life (Short-Form 36 and EuroQol-5D), time to resumption of ADL/work, and cost-effectiveness. Data will be analyzed using univariate and multivariable analyses (including mixed effects regression analysis). The cost-effectiveness analysis will be performed from a societal perspective. DISCUSSION: Successful completion of this trial will provide evidence on the effectiveness of operative versus non-operative treatment of patients with a humeral shaft fracture. TRIAL REGISTRATION: The trial is registered at the Netherlands Trial Register (NTR3617)