Fosfaatbehoefte van bloembollen; onderbouwing van de fosfaatbemestingsadviezen

De fosfaatbemestingsadviezen voor bloembollen zijn in de periode 1996-2002 onderwerp van onderzoek geweest. De aanleiding daartoe werd gevormd door het feit dat het fosfaatoverschot op bedrijfniveau knelt met het toegelaten overschot volgens MINAS en omdat het advies zwak onderbouwd en gedateerd is. De meststofbehoefte van bolgewassen afhankelijk van de fosfaattoestand van de bodem is vastgesteld. Verder is onderzocht welke fosfaattoestand nagestreefd dient te worden en hoe fosfaatbemesting afgestemd kan worden op de fosfaattoestand zonder in conflict te komen met de milieukwaliteitsdoelstellingen. Een nieuw bemestingsadvies is opgesteld gebaseerd op een combinatie van veld- en procesonderzoek. In het algemeen reageren bolgewassen in vergelijking met andere gewassen weinig of niet op fosfaattoestand en fosfaatbemesting. Strikte evenwichtsbemesting volgens `aanvoer is afvoer¿ volstaat bij de meeste bolgewassen. Reparatiebemesting van een te lage fosfaattoestand van duinzand volgens generieke normen leidt tot verhoogd risico op uitspoeling omdat deze grondsoort zeer zwakke bufferende eigenschappen bezit. Op dergelijke gronden verdient het uit milieuoverwegingen aanbeveling geen reparatiebemesting uit te voeren

Characterization of plaque components with intravascular ultrasound elastography in human femoral and coronary arteries in vitro

BACKGROUND: The composition of plaque is a major determinant of coronary-related clinical syndromes. Intravascular ultrasound (IVUS) elastography has proven to be a technique capable of reflecting the mechanical properties of phantom material and the femoral arterial wall. The aim of this study was to investigate the capability of intravascular elastography to characterize different plaque components. METHODS AND RESULTS: Diseased human femoral (n=9) and coronary (n=4) arteries were studied in vitro. At each location (n=45), 2 IVUS images were acquired at different intraluminal pressures (80 and 100 mm Hg). With the use of cross-correlation analysis on the high-frequency (radiofrequency) ultrasound signal, the local strain in the tissue was determined. The strain was color-coded and plotted as an additional image to the IVUS echogram. The visualized segments were stained on the presence of collagen, smooth muscle cells, and macrophages. Matching of elastographic data and histology were performed with the use of the IVUS echogram. The cross sections were segmented in regions (n=125) that were based on the strain value on the elastogram. The dominant plaque types in these regions (fibrous, fibro-fatty, or fatty) were obtained from histology and correlated with the average strain and echo intensity. The strain for the 3 plaque types as determined by histology differed significantly (P=0.0002). This difference was mainly evident between fibrous and fatty tissue (P=0.0004). The plaque types did not reveal echo-intensity differences in the IVUS echogram (P=0.882). CONCLUSIONS: Different strain values are found between fibrous, fibro-fatty, and fatty plaque components, indicating the potential of intravascular elastography to distinguish different plaque morphologies

Current Status of Clinical Magnetic Resonance Imaging for Plaque Characterisation in Patients with Carotid Artery Stenosis

AbstractObjectiveThe article aims to provide an overview of the literature that assessed the agreement between magnetic resonance imaging (MRI) and histology for specific carotid plaque characteristics associated with vulnerability in terms of sensitivity and specificity.MethodsA systematic search strategy was conducted in MEDLINE and EMBASE databases resulting in 1084 articles. Finally, we included 17 papers. Due to variation in presentation, especially in MRI and histology methods, a pooled analysis could not be performed.ResultsTwo studies were performed on a 3.0-T MRI scanner; all other studies were performed on a 1.5-T scanner. Most performed sequences were two-dimensional (2D) and three-dimensional (3D) T1-weighted and all histology protocols varied slightly. Our results indicate that calcification, fibrous cap, intraplaque haemorrhage and lipid-rich necrotic cores can be identified with moderate-to-good sensitivity and specificity.ConclusionsBased on current literature, it appears premature for routine application of MRI as an imaging modality to assess carotid plaque characteristics associated with plaque vulnerability. Although MRI still holds promise, clinical application for plaque characterisation would require consensus regarding MRI settings and confirmation by histology. Predefined protocols for histology and MR imaging need to be established

Atherosclerotic Plaque Stability Is Affected by the Chemokine CXCL10 in Both Mice and Humans.

Background. The chemokine CXCL10 is specifically upregulated during experimental development of plaque with an unstable phenotype. In this study we evaluated the functional consequences of these findings in mice and humans. Methods and Results. In ApoE(-/-) mice, we induced unstable plaque with using a flow-altering device around the carotid artery. From week 1 to 4, mice were injected with a neutralizing CXCL10 antibody. After 9 weeks, CXCL10 inhibition resulted in a more stable plaque phenotype: collagen increased by 58% (P = 0.002), smooth muscle cell content increased 2-fold (P = 0.03), while macrophage MHC class II expression decreased by 50% (P = 0.005). Also, the size of necrotic cores decreased by 41% (P = 0.01). In 106 human carotid endarterectomy specimens we found that increasing concentrations of CXCL10 strongly associate with an increase in atheromatous plaque phenotype (ANOVA, P = 0.003), with high macrophage, low smooth muscle cell, and low collagen content. Conclusions. In the present study we showed that CXCL10 is associated with the development of vulnerable plaque in human and mice. We conclude that CXCL10 might provide a new lead towards plaque-stabilizing therapy

The relationship between fractional flow reserve, platelet reactivity and platelet leukocyte complexes in stable coronary artery disease

Background: The presence of stenoses that significantly impair blood flow and cause myocardial ischemia negatively affects prognosis of patients with stable coronary artery disease. Altered platelet reactivity has been associated with impaired prognosis of stable coronary artery disease. Platelets are activated and form complexes with leukocytes in response to microshear gradients caused by friction forces on the arterial wall or flow separation. We hypothesized that the presence of significantly flow-limiting stenoses is associated with altered platelet reactivity and formation of platelet-leukocyte complexes. Methods: One hundred patients with stable angina were studied. Hemodynamic significance of all coronary stenoses was assessed with Fractional Flow Reserve (FFR). Patients were classified FFR-positive (at least one lesion with FFR 0.80). Whole blood samples were stimulated with increasing concentrations of ADP, TRAP, CRP and Iloprost with substimulatory ADP. Expression of P-selectin as platelet activation marker and platelet-leukocyte complexes were measured by flowcytometry. Patients were stratified on clopidogrel use. FFR positive and negative patient groups were compared on platelet reactivity and platelet-leukocyte complexes. Results: Platelet reactivity between FFR-positive patients and FFR-negative patients did not differ. A significantly lower percentage of circulating platelet-neutrophil complexes in FFR-positive patients and a similar non-significant decrease in percentage of circulating platelet-monocyte complexes in FFR-positive patients was observed. Conclusion: The presence of hemodynamically significant coronary stenoses does not alter platelet reactivity but is associated with reduced platelet-neutrophil complexes in peripheral blood of patients with stable coronary artery disease