A successful intervention to improve conceptual knowledge of medical students who rely on memorization of disclosed items.

Background: The mere memorization of isolated facts without the claim of integrating them is detrimental to the desired learning outcomes in medical education. The current study was conducted within an environment where items from summative assessments are regularly disclosed by the university and consequently collected into an item bank that is shared between students. Within this environment, we aimed to quantify 1) to which extent students use disclosed items for their preparation for the summative exam, 2) a putative mismatch between (isolated factual) knowledge regarding distinct questions from the item bank and conceptual knowledge, and 3) to which extent this mismatch can be ameliorated by a project aiming to steer student learning away from the memorization of isolated facts toward the acquisition of conceptual knowledge. Methods: This steering project in the midst of the first semester consisted of the implementation of an oral exam based on selected learning objectives, preceded by two seminars. After their summative exam at the end of semester, 135 students performed a voluntary exam for study purposes. Here, authentic (i.e., presumably preknown) physiology questions taken from the item bank were used to assess students' ability to 1) recognize the correct answer in a multiple choice (MC) question, 2) recall the answer (short answer), or 3) display conceptual knowledge closely corresponding to the question presented in the other formats. Additionally, students received a questionnaire addressing their learning habits and attitudes. Results: The median reported percentage of learning time for the summative exam exclusively spent with this item bank was 80%. The results of the voluntary exam indicate that students frequently recognize and recall correct answers of included items without displaying knowledge of the underlying concept. Compared to recall of the correct answer, the probability of giving a correct answer regarding the corresponding basal physiologic concept was lower by 47 percentage points (p <0.001) for topics not included in the steering project. Regarding topics included in the steering project, this discrepancy was reduced to 25.5% (p <0.001). Conclusion: The results of this study demonstrate the influence of disclosed items on student learning and learning outcomes and suggest that a carefully implemented assessment is able to improve conceptual knowledge in physiology.

Effects of high-intensity interval training on trajectories of gas-exchange measures and blood lactate concentrations during cardiopulmonary exercise tests in cardiac rehabilitation-A randomized controlled trial.

BACKGROUND: The optimal allocation of training time to different intensities in cardiac rehabilitation is still under debate. The objective of this study was to explore whether in a 12-week cardiac rehabilitation program, replacement of two of four usual continuous endurance training (CET) sessions per week with energy expenditure-matched high-intensity interval training (HIIT) affects the trajectories of cardiopulmonary exercise test (CPET) variables such as ventilatory equivalents for O2 (EqO2 ) and CO2 (EqCO2 ), and blood lactate (BLa) during CPET. METHODS: Eighty-two male patients undergoing outpatient cardiac rehabilitation after an acute coronary syndrome were randomized to CET (age [mean ± SD] 61.7 ± 9.8 years, body mass index [BMI] 28.1 ± 3.4) or HIIT+CET (60.0 ± 9.4 years, BMI 28.5 ± 3.5). CPET was performed at baseline, after 6 and after 12 weeks. HIIT consisted of ten 60-s bouts of cycling at an intensity of 100% of the maximal power output (Pmax ) achieved in an incremental test to exhaustion, interspersed with 60 s at 20% Pmax . CET was performed at 60% Pmax with equal duration. Training intensities were adjusted after 6 weeks to account for the training-induced improvement in cardiorespiratory fitness. The entire functions defining the relationship between EqO2 , EqCO2 , and BLa, with power output were modeled using linear mixed models to assess how these trajectories are affected by HIIT. RESULTS: After 6 and 12 weeks, Pmax increased to 112.9% and 117.5% of baseline after CET, and to 113.9% and 124.7% after HIIT+CET (means). Twelve weeks of HIIT+CET elicited greater reductions of EqO2 and EqCO2 than CET alone (p < 0.0001 each) in a range above 100% baseline Pmax . Specifically, at 100% of baseline Pmax , least squares arithmetic mean EqO2 values of CET and HIIT+CET patients were 36.2 versus 33.5. At 115% and 130% of baseline Pmax , EqO2 values were 41.2 versus 37.1 and 47.2 versus 41.7. Similarly, corresponding EqCO2 values of CET and HIIT+CET patients were 32.4 versus 31.0, 34.3 versus 32.2, and 37.0 versus 34.0. Conversely, mean BLa levels (mM) were not differently affected (p = 0.64). At 100%, 115%, and 130% of baseline Pmax after 12 weeks, BLa levels did not differ to a relevant extent (least squares geometric means, 3.56 vs. 3.63, 5.59 vs. 5.61, 9.27 vs. 9.10). CONCLUSIONS: While HIIT+CET reduced ventilatory equivalents more effectively than CET alone, specifically when patients were approaching their maximal performance during CPET, both training strategies were equally effective in reducing BLa levels.

Platelet Activation Is Not Always Associated With Platelet-Related Plasma microRNA Abundance - Results From a Randomized Controlled Trial of Periodontal Patients.

Platelets are involved in a variety of diseases, making their adequate functional assessment is essential. However, due to their easily activatable nature this has some methodological pitfalls. Therefore, the availability of stable, easily measurable surrogate markers would be beneficial. In this regard, some evidence suggests that certain microRNAs (miRNAs) circulating in plasma might be useful. We aimed to corroborate their suitability by analyzing plasma samples obtained in a randomized controlled trial, which assessed the effects of periodontal treatment on platelet function. We hypothesized that miRNA levels mirror changes of platelet activation and -function. Both platelet function and miRNA abundance were quantified using state-of-the-art flow cytometry and qPCR methods. The following miRNAs were quantified: 223-3p, 150-5p, 197-3p, 23a-3p, 126-3p, 24-3p, 21-5p, 27b-3p, 33a-5p, 320a, 191-5p, 28-3p, 451a, 29b-3p, and 1-3p. However, periodontal treatment did not affect the abundance of any investigated miRNAs to a relevant extent. Platelet activation and reactivity indices did neither correlate with any tested miRNA at baseline, nor after the treatment period. In addition, there was no evidence that investigated miRNAs were released by platelets, as suggested previously. In conclusion, our data suggest that in patients suffering from periodontal disease the investigated miRNAs are unlikely to be suitable biomarkers for platelet function. Our data aim to raise awareness that previously determined platelet activation dependent circulating miRNAs are not suitable as platelet biomarkers in all cohorts.

Implementation of a visual raise hand function in PowerPoint®.

Objective: Replacing face-to-face lessons by remote teaching due to COVID-19 led to a markedly reduced interaction between students and lecturers. In our opinion, one of the main reasons for this is the raise hand function of the respective web conference systems, which (independent of the system used) results in an unobtrusive signal that can easily be missed by the lecturer. Given the necessary focus on one's own presentation, questions can therefore only be perceived with a considerable time delay and can only be integrated into the lessons to a limited extent. Thus, the idea arose to display question requests of the auditorium by a clear visual signal in PowerPoint® itself. Methodology: With Visual Basic for Applications (VBA), Microsoft PowerPoint® holds an integrated programming language that extends its functionality. Accordingly, VBA was used to program a routine running in the background of the presentation, which periodically retrieves the contents of a web-based "signal file" in a cycle of a few seconds. The content of this signal file, in turn, can be modified by the students by calling up an URL (i.e. from any Internet-capable device) - this results in a (customizable) visual signal in PowerPoint® that is temporarily visible and does not further interfere with the presentation. Conclusion: With the concept presented here, a raise hand function was realized in PowerPoint®, which manifests itself as a clear visual signal independent of the web conferencing system used. This enables the lecturers to respond instantly to questions from the audience during live transmission of lectures.

Distance teaching of experimental scientific methodology and scientific thinking.

Objective: The aim of this project was to convert a traditional face-to-face seminar for the teaching of experimental scientific methodology to remote teaching in a timely manner due to the COVID-19 related restrictions to teaching in presence. Methodology: The main focus of the course was on flow cytometry. Basics were developed in a virtual presence phase. Specific teaching contents were taught by an interactive presentation, which came very close to the user experience of a flow cytometer and interactively illustrated the influence of different experimental conditions on the obtained results. Video sequences of authentic sample acquisitions were integrated into Adobe Captivate®. These "virtual acquisitions" were not distinguishable from the original procedure. For interpretation of the resulting diagrams, interactions were inserted, which allowed direct comparison of the obtained results. Implementation: A presentation with interactive elements and video sequences was created and used for the virtual presence phases. After publishing on a web server in HTML 5, contents were made available to the students for post-processing of learning contents by self-paced learning with full (interactive) functionality. Conclusion: Contributions elaborated by the students during the course demonstrate a learning outcome comparable to that archieved in the last years in presence mode. While implementation of this solution represented a highly time-consuming process, narrative feedback was consistently positive. Due to the short time available for implementation, no systematic evaluation could be conducted, which represents a clear limitation of this work.

CD36-fibrin interaction propagates FXI-dependent thrombin generation of human platelets.

Thrombin converts fibrinogen to fibrin and activates blood and vascular cells in thrombo-inflammatory diseases. Platelets are amplifiers of thrombin formation when activated by leukocyte- and vascular cell-derived thrombin. CD36 on platelets acts as sensitizer for molecules with damage-associated molecular patterns, thereby increasing platelet reactivity. Here, we investigated the role of CD36 in thrombin-generation on human platelets, including selected patients with advanced chronic kidney disease (CKD). Platelets deficient in CD36 or blocked by anti-CD36 antibody FA6.152 showed impaired thrombin generation triggered by thrombin in calibrated automated thrombography. Using platelets with congenital function defects, blocking antibodies, pharmacological inhibitors, and factor-depleted plasma, CD36-sensitive thrombin generation was dependent on FXI, fibrin, and platelet signaling via GPIbα and SFKs. CD36-deficiency or blocking suppressed thrombin-induced platelet αIIbß3 activation, granule exocytosis, binding of adhesion proteins and FV, FVIII, FIX, FX, but not anionic phospholipid exposure determined by flow cytometry. CD36 ligated specifically soluble fibrin, which recruited distinct coagulation factors via thiols. Selected patients with CKD showed elevated soluble fibrin plasma levels and enhanced thrombin-induced thrombin generation, which was normalized by CD36 blocking. Thus, CD36 is an important amplifier of platelet-dependent thrombin generation when exposure of anionic phospholipids is limited. This pathway might contribute to hypercoagulability in CKD.

Effects of high-intensity interval training on platelet function in cardiac rehabilitation: a randomised controlled trial.

OBJECTIVE: To compare effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on platelet function in patients undergoing cardiac rehabilitation, as hyper-reactive platelets are involved in atherogenesis and atherothrombosis. METHODS: In this single-centre parallel group randomised controlled trial, male patients after an acute coronary syndrome under dual antiplatelet therapy performed MICT or HIIT+MICT for 12 weeks. Main outcome was platelet reactivity measured by the half-maximal concentration (EC50) of platelet agonist thrombin receptor-activating peptide-6 (TRAP-6) in terms of P-selectin expression. EC50 was determined at baseline, after 6 and 12 weeks, each time at physical rest and on exertion. RESULTS: 82 patients were randomised to MICT or HIIT+MICT. Mean (95% CI) baseline EC50values at physical rest were 6.7 µM (6.3 µM to 7.0 µM) TRAP-6. After 6/12 weeks, 36/33 MICT and 34/28 HIIT+MICT patients were examined. HIIT+MICT patients had 0.9 µM (0.4 µM to 1.4 µM)/0.5 µM (-0.1 µM to 1.0 µM) higher EC50values than MICT ones, and the propensity of their platelets to form aggregates with monocytes was significantly lower after 12 weeks. Short-term strenuous physical exertion was generally associated with platelet activation and an EC50reduction of 0.7 µM (0.6 µM to 0.8 µM). HIIT+MICT patients tended to be fitter after 12 weeks. No serious harms were observed. CONCLUSIONS: Including HIIT in cardiac rehabilitation seems to confer additional benefits compared with MICT alone, which should be confirmed in clinical trials with hard endpoints. Exertion-induced platelet activation and hyper-reactivity occur despite dual antiplatelet therapy. TRIAL REGISTRATION NUMBER: NCT02930330; Results.

Periodontal treatment does not result in detectable platelet activation in vivo.

OBJECTIVES: Periodontitis is associated with systemic inflammation, elevated platelet activation and enhanced risk for cardiovascular diseases, while periodontal treatment reduces tissue inflammation and shows desirable effects on the oral biofilm and dental health. However, subgingival debridement during conservative treatment can lead to local trauma and transient bacteraemia, which might affect cardiovascular risk in these patients. Therefore, we investigated the effect of periodontal treatment on systemic platelet activation. MATERIALS AND METHODS: In a prospective therapeutic trial, 26 patients underwent periodontal treatment and patient blood was analysed immediately before and immediately after intervention for platelet activation markers (flow cytometric analysis of P-selectin, CD63 and CD40L surface expression, integrin αIIbß3 activation and fibrinogen binding, intra-platelet reactive oxygen species production, platelet-leukocyte aggregate formation and intra-platelet vasodilator-stimulated phosphoprotein phosphorylation) in response to adenosine diphosphate (ADP). RESULTS: The present study shows that basal platelet activation levels remain largely unaltered in response to periodontal treatment. We also did not observe significant changes in platelet reactivity in response to different concentrations of platelet agonist ADP. CONCLUSION: Subgingival debridement does not result in relevantly elevated platelet activation. Thus, augmented platelet activation seems unlikely to be a causative triggering factor that increases the short-term risk for platelet-mediated thrombotic events in response to subgingival debridement. CLINICAL RELEVANCE: Subgingival debridement is a safe procedure and does not increase the short-term risk for platelet-mediated thrombotic events.

Exercise-based cardiac rehabilitation is associated with a normalization of the heart rate performance curve deflection.

The heart rate (HR) rises with increased power output, whereby in most healthy individuals, the slope of HR levels off with higher intensity. This corresponds to a downward deflection of the heart rate performance curve (HRPC). Conversely, in patients after myocardial infarction, an upward HRPC deflection is frequently observed that is especially pronounced in patients with compromised left ventricular ejection fraction. To investigate whether regular endurance training during cardiac rehabilitation might normalize HRPC, data of 128 male patients were analyzed. All patients performed three exercise tests: at baseline, after 6 weeks, and after 1 year. Ninety-six patients exercised regularly according to guidelines for 1 year (training group, TG), and 32 stopped after 6 weeks (control group, CG). Similarly, upward-deflected HRPCs were observed at baseline and after 6 weeks in both groups. After 1 year, TG patients had less upward-deflected HRPCs compared with CG ones, corresponding to a partial normalization. Greater changes in HRPC deflection were associated with larger improvements in cardiorespiratory fitness. Our results might indicate improved myocardial function due to long-term rehabilitation. Further, HRPC alterations over time should be considered when prescribing exercise intensities using a target HR, as deflection flattening might render the intensity of corresponding exercise insufficient.

Periodontal treatment limits platelet activation in patients with periodontitis-a controlled-randomized intervention trial.

AIM: Periodontitis results in platelet activation and enhanced risk for cardiovascular disease. As it is currently unknown whether periodontal treatment reverses platelet hyper-reactivity, we aimed to investigate the role of periodontal treatment on platelet activation. MATERIALS AND METHODS: In a prospective controlled therapeutic trial, 52 patients were enrolled and randomly selected for periodontal treatment or monitored without treatment for 3 months. Patient blood was analysed by flow cytometry for platelet activation markers and by light transmission aggregometry for platelet aggregation in response to pro-thrombotic stimuli. RESULTS: In this study, platelet activation in the control group aggravated over the observation period of 3 months, whereas patients that underwent periodontal treatment showed unchanged levels of platelet activation, measured by surface expression of CD62P, CD40L, generation of reactive oxygen production, activation of GPIIb/IIIa and fibrinogen binding. Moreover, platelet turnover, measured by platelet RNA content and platelet aggregation in response to collagen, differed significantly between patients that were treated and those who were untreated. CONCLUSIONS: Subgingival debridement reduces the risk of aggravated platelet activation and therefore might potentially diminish subsequent diseases such as cardiovascular disease in periodontal patients.

Serum levels of 25-hydroxyvitamin D are associated with periodontal disease.

OBJECTIVES: Vitamin D plays an essential role in bone metabolism as well as in immunity. Hence, it might affect the development and extent of periodontal disease. The aim of this study was the assessment of 25-hydroxyvitamin D (25(OH)D) status in periodontal disease. MATERIALS AND METHODS: Twenty-nine patients with severe periodontal disease and 29 healthy volunteers were recruited in this case-control-study. Serum 25(OH)D levels, Periodontal Probing Depth (PPD), Clinical Attachment Level (CAL), Bleeding on Probing (BOP), Body Mass Index (BMI), and current smoking status and smoking history (packyears) were assessed in all participants. Serum 25(OH)D levels were compared between controls and cases. Multivariable logistic regression was used to determine the odds ratio (OR) and 95 % confidence interval (CI) for periodontal disease in 25(OH)D deficient probands. RESULTS: Patients with periodontal disease presented a significantly higher proportion of deficient 25(OH)D levels (i.e., <50 nmol/l) compared to healthy controls (48 vs. 14 % respectively). The adjusted OR for periodontal disease with vitamin D deficiency was 1.5 (95 % CI, 1.13-1.98). No correlation between serum 25(OH)D levels and CAL, PPD, and BOP in the group with periodontal disease was found. CONCLUSIONS: In this case-control-study 25(OH)D deficiency is significantly associated with periodontal disease. CLINICAL RELEVANCE: The assessment of vitamin D levels in patients presenting with periodontal disease seems advisable, as vitamin D deficiency might be involved in the onset and progression of periodontal disease.

Correlation between Cardiorespiratory Fitness and Platelet Function in Healthy Women.

PURPOSE: Low cardiorespiratory fitness (CRF) represents a major risk factor for atherosclerosis, and platelets play a key role in the development of this chronic inflammatory disease. Therefore, the purpose of this study was to assess the relationship between CRF and platelet function. METHODS: CRF and different aspects of platelet function were assessed in healthy, young, nonsmoking women. Results were compared between groups of low (LF), medium (MF) and high CRF (HF). Measurements were repeated in group LF after a supervised endurance training program lasting two menstrual cycles and obtained results were compared with groups MF and HF. CRF was quantified by maximal oxygen consumption (V˙O2max) determined by an incremental treadmill exercise test. V˙O2max criteria for groups were (mL·min·kg bodyweight): LF < 45, MF 45-55, HF > 55. Platelet activation state and platelet reactivity were assessed by basal and agonist-induced surface expression of CD62P and CD40L as well as the intraplatelet amount of reactive oxygen species. RESULTS: In group LF, basal platelet activation as well as agonist-induced platelet reactivity were increased compared with groups MF and HF. Between groups MF and HF parameters of platelet function were roughly equal despite a pronounced difference regarding CRF. Exercise training improved CRF in group LF and aligned platelet function to levels observed in groups MF and HF, although CRF still markedly differed. CONCLUSIONS: Low levels of CRF favor a proinflammatory platelet phenotype. A relatively low dose of exercise is sufficient to normalize platelet function, whereas superior levels of physical activity and CRF do not provide any further substantial benefit, but also no appreciable adverse effects.

Effects of Physical (In)activity on Platelet Function.

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

A novel, rapid method to quantify intraplatelet calcium dynamics by ratiometric flow cytometry.

Cytosolic free calcium ions represent important second-messengers in platelets. Therefore, quantitative measurement of intraplatelet calcium provides a popular and very sensitive tool to evaluate platelet activation and reactivity. Current protocols for determination of intracellular calcium concentrations in platelets have a number of limitations. Cuvette-based methods do not allow measurement of calcium flux in complex systems, such as whole blood, and therefore require isolation steps that potentially interfere with platelet activation. Flow cytometry has the potential to overcome this limitation, but to date the application of calibrated, quantitative readout of calcium kinetics has only been described for Indo-1. As excitation of Indo-1 requires a laser in the ultraviolet range, such measurements cannot be performed with a standard flow cytometer. Here, we describe a novel, rapid calibration method for ratiometric calcium measurement in platelets using both Ar(+)-laser excited fluorescence dyes Fluo-4 and Fura Red. We provide appropriate equations that allow rapid quantification of intraplatelet calcium fluxes by measurement of only two standardisation buffers. We demonstrate that this method allows quantitative calcium measurement in platelet rich plasma as well as in whole blood. Further, we show that this method prevents artefacts due to platelet aggregate formation and is therefore an ideal tool to determine basal and agonist induced calcium kinetics.

Platelets mediate oxidized low-density lipoprotein-induced monocyte extravasation and foam cell formation.

OBJECTIVE: A growing body of evidence indicates that platelets contribute to the onset and progression of atherosclerosis by modulating immune responses. We aimed to elucidate the effects of oxidized low-density lipoprotein (OxLDL) on platelet-monocyte interactions and the consequences of these interactions on platelet phagocytosis, chemokine release, monocyte extravasation, and foam cell formation. APPROACH AND RESULTS: Confocal microscopy and flow cytometric analysis revealed that in vitro and in vivo stimulation with OxLDL resulted in rapid formation of platelet-monocyte aggregates, with a preference for CD16+ monocyte subsets. This platelet-monocyte interaction facilitated OxLDL uptake by monocytes, in a process that involved platelet CD36-OxLDL interaction, release of chemokines, such as CXC motif ligand 4, direct platelet-monocyte interaction, and phagocytosis of platelets. Inhibition of cyclooxygenase with acetylsalicylic acid and antagonists of ADP receptors, P2Y1 and P2Y12, partly abrogated OxLDL-induced platelet-monocyte aggregates and platelet-mediated lipid uptake in monocytes. Platelets also enhanced OxLDL-induced monocyte transmigration across an endothelial monolayer via direct interaction with monocytes in a transwell assay. Importantly, in LDLR(-/-) mice, platelet depletion resulted in a significant decrease of peritoneal macrophage recruitment and foam cell formation in a thioglycollate-elicited peritonitis model. In platelet-depleted wild-type mice, transfusion of ex vivo OxLDL-stimulated platelets induced monocyte extravasation to a higher extent when compared with resting platelets. CONCLUSIONS: Our results on OxLDL-mediated platelet-monocyte aggregate formation, which promoted phenotypic changes in monocytes, monocyte extravasation and enhanced foam cell formation in vitro and in vivo, provide a novel mechanism for how platelets potentiate key steps of atherosclerotic plaque development and plaque destabilization.

Myocardial dimensions and hemodynamics during 24-h ultraendurance ergometry.

PURPOSE: This study aimed to evaluate cardiorespiratory and hemodynamic responses during 24 h of continuous cycle ergometry in ultraendurance athletes. METHODS: Eight males (mean ± SD; age = 39 ± 8 yr, height = 179 ± 7 cm, body weight [Wt] = 77.1 ± 6.0 kg) were monitored during 24 h at a constant workload,∼25% below the first lactate turn point at 162 ± 23 W. Measurements included Wt, HR, oxygen consumption (V˙O2), cardiac output (Q), and stroke volume (SV) determined by a noninvasive rebreathing technique (Innocor; Innovision, Odense, Denmark). Myocardial dimensions were evaluated using a two-dimensional echocardiogram. [M-mode measurement]-left atrial (LAD), ventricular end-diastolic (LVEDD), and end-systolic diameters (LVESD) were obtained over the left parasternal area. Venous blood samples were analyzed for hematocrit (Hct%), albumin (g·L(-1)), aldosterone (pg·mL(-1)), CK, CK-MB (U·L(-1)), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (pg·mL(-1)). RESULTS: HR (bpm) significantly increased (P < 0.01) from 1 h (132 ± 11) to 6 h (143 ± 10) and significantly decreased (P < 0.001) from 6 to 24 h (116 ± 10). V˙O2 and (Q were unchanged during the 24 h. Wt (76.6 ± 5.6 vs 78.7 ± 5.4), SV (117 ± 13 vs 148 ± 19), LVEDD (4.9 ± 0.3 vs 5.6 ± 0.2), and LAD (3.6 ± 0.5 vs 4.3 ± 0.7) significantly increased between 6 and 24 h (P < 0.001). No significant changes were observed for LVESD. Hct (45.1 ± 1.3 vs 41.3 ± 1.2) significantly decreased (P < 0.05) and CK (181 ± 60/877 ± 515), aldosterone (48 ± 17 vs 661 ± 172), and NT-proBNP (23 ± 13 vs 583 ± 449) significantly increased (P < 0.05). The increase in SV (ΔSV) was significantly related to changes in Wt (ΔWt), and HR (ΔHR) and ΔWt were significantly related to ΔLAD and ΔLVEDD. CONCLUSION: Our findings suggest that the decrease in HR during 24 h of ultraendurance exercise was due to hypervolemia and the associated ventricular loading, increasing left ventricular diastolic dimensions because of increased SV and LVEDD, resulting in an increase in NT-proBNP.

Native high density lipoproteins (HDL) interfere with platelet activation induced by oxidized low density lipoproteins (OxLDL).

Platelets and lipoproteins play a crucial role in atherogenesis, in part by their ability to modulate inflammation and oxidative stress. While oxidized low density lipoproteins (OxLDL) play a central role in the development of this disease, high density lipoproteins (HDL) represent an atheroprotective factor of utmost importance. As platelet function is remarkably sensitive to the influence of plasma lipoproteins, it was the aim of this study to clarify if HDL are able to counteract the stimulating effects of OxLDL with special emphasis on aspects of platelet function that are relevant to inflammation. Therefore, HDL were tested for their ability to interfere with pro-thrombotic and pro-inflammatory aspects of platelet function. We are able to show that HDL significantly impaired OxLDL-induced platelet aggregation and adhesion. In gel-filtered platelets, HDL decreased both the formation of reactive oxygen species and CD40L expression. Furthermore, HDL strongly interfered with OxLDL-induced formation of platelet-neutrophil aggregates in whole blood, suggesting that platelets represent a relevant and sensitive target for HDL. The finding that HDL effectively competed with the binding of OxLDL to the platelet surface might contribute to their atheroprotective and antithrombotic properties.

Iron deficiency generates secondary thrombocytosis and platelet activation in IBD: the randomized, controlled thromboVIT trial.

BACKGROUND: Secondary thrombocytosis is a common clinical feature. In patients with cancer, it is a risk factor for venous thromboembolic events. In inflammatory bowel disease (IBD), thrombocytosis is so far considered a marker of active disease and may contribute to the increased thromboembolic risk in this population. Observed effects of iron therapy on normalization of platelet counts led us to hypothesize that iron itself may regulate megakaryopoiesis. Here, we want to test the effect of iron replacement on platelet count and activity in IBD-associated thrombocytosis. METHODS: We performed a randomized, single-blinded placebo-controlled trial testing the effect of ferric carboxymaltose (FCM) in patients with IBD with secondary thrombocytosis (platelets > 450 G/L). Changes in platelet counts, hemoglobin, iron parameters, disease activity, megakaryopoietic growth factors, erythropoietin, and platelet activity were assessed. Patients received placebo or up to 1500 mg iron as FCM. Endpoints were evaluated at week 6. RESULTS: A total of 26 patients were included in the study, 15 patients were available for the per protocol analysis. A drop in platelets >25% (primary endpoint) was observed in 4 of 8 (50%, iron group) and 1 of 7 patients (14%, placebo group, P = 0.143). Mean platelet counts dropped on FCM but not on placebo (536 G/L to 411 G/L versus 580 G/L to 559 G/L; P = 0.002). Disease activity and megakaryopoietic growth factors remained unchanged and hemoglobin and iron parameters increased on FCM. The normalization of platelet counts was associated with a decrease in platelet aggregation and P-selectin expression. CONCLUSION: FCM lowers platelet counts and platelet activation in patients with IBD-associated secondary thrombocytosis.

Platelets directly enhance neutrophil transmigration in response to oxidised low-density lipoprotein.

Beyond their primary role in haemostasis and tissue repair, platelets are causally involved in the onset of inflammatory reactions, cell proliferation and immune response. Platelet activation and platelet binding to the endothelium result in release of chemokines and increased expression of adhesion molecules, which promote the recruitment of leukocytes that will eventually migrate across the endothelium into the tissue. Here, we provide the first evidence that platelets stimulated with oxidised low-density lipoprotein (oxLDL) directly enhance recruitment and transmigration of neutrophils, via cell-cell interaction. OxLDL immediately activates platelets, which then rapidly bind to neutrophils, foster their activation and facilitate transmigration through an endothelial monolayer. The observed effects of oxLDL on platelet-neutrophil aggregate (PNA) formation depend on incubation time, lipoprotein concentration and the degree of oxidative modification of LDL. PNA form within minutes following stimulation by oxLDL and remain for up to 1 h post stimulation, while native LDL is unable to induce platelet-neutrophil interactions. In the presence of acetylsalicylic acid the formation of PNA in response to oxLDL is virtually absent, and platelets fail to further enhance oxLDL-induced neutrophil transmigration. P2Y1 and P2Y12 inhibitors have less pronounced effects on PNA formation in response to oxLDL. Furthermore, we demonstrate that the PI3K pathway is essential for efficient neutrophil transmigration induced by oxLDL. Consequently, platelets enhance neutrophil transmigration in response to oxLDL and might thereby contribute essentially to the amplification of inflammatory processes within the vessel wall, which fosters the development of atherosclerosis.

Periodontopathogens induce expression of CD40L on human platelets via TLR2 and TLR4.

INTRODUCTION: The outstanding importance of (soluble) CD40L to cardiovascular disease (CVD) is becoming increasingly apparent as CD40L is an important mediator of thrombotic and inflammatory processes. Platelets are the main source for CD40 ligand, linking platelet stimulatory events to inflammation and adverse adaptive immune responses. Periodontitis represents a chronic dental infection by distinct gram negative bacteria that is associated with an increased risk for CVD. However, the effects of periodontopathogens on CD40L expression by platelets have not been determined. MATERIAL AND METHODS: Effects of periodontopathogens A. actinomycetemcomitans Y and P. gingivalis on the expression of CD40L were determined and the underlying receptors and pathways were investigated. 26 patients with periodontitis and 19 controls were included in the clinical part of this study. RESULTS: Periodontopathogens directly induce surface expression of CD40L in human platelets. This activation depends on plasma factors like CD14 and involves TLR2 and TLR4 but not FcγRII. Inhibition of PI3K and PLC completely abolishes bacteria-induced surface expression of CD40L. TLR2 and TLR4 agonists, for example, are also able to induce expression and release of CD40L in human platelets. In patients with periodontitis, plasma levels of soluble CD40L are elevated and positivity for P. gingivalis is associated with a statistical significant increase of soluble CD40L. CONCLUSIONS: Our data indicate an involvement of periodontopathogens in increased plasma levels of soluble CD40L in periodontitis and therefore provide a novel link between periodontitis and increased risk for CVD.