Relation entre germination, mise à fleurs et niveau de prélèvement des semenceaux d'ignames du complexe Dioscorea cayenensis-rotundata

La présente étude met en évidence la précocité des semenceaux de tête pour la levée de germination chez l'ensemble des variétés de #Dioscorea cayenensis-rotundata$ étudiées. Chez la variété Afoubessou, on observe un gradient de levée, allant de la tête vers la base. Pour les autres variétés, il n'y a pas de différence signicative entre les semenceaux du milieu et de la base de la semence-mère. L'étude de l'ensemble des variétés indique une précocité de levée des femelles comparativement aux plantes mâles. Pour la mise à fleurs, un effet du niveau de prélèvement des semenceaux est mis en évidence chez les variétés Gnan et Afoubessou, avec une précocité marquée chez les plantes issues de la base. Les droites de régression suivies du test de parallélisme montrent clairement chez la variété Gnan, que le délai de floraison est plus court chez les plantes qui lèvent tardivement. Ainsi est mise en évidence l'existence d'"une programmation" fixe de la date d'initiation de la floraison, indépendamment des différents facteurs réglant la levée. Avec l'ensemble des variétés étudiées, la floraison est plus précoce chez les mâles que chez les femelles. Mais la grande variabilité des dates de floraison existant au sein des variétés permet une synchronisation de la mise à fleurs entre certaines variétés mâles et certaines variétés femelles. (Résumé d'auteur

Effects of Spin on Tennis Ball Aerodynamics: An Experimental and Computational Study

The aerodynamic behaviour of a tennis ball is very complex and significantly differs from other sports balls due to its surface structures (fuzz, seam orientation etc). Relatively high rotational speeds (spin) make the aerodynamic properties of tennis balls even more complex. Although several studies have been conducted on drag and lift in steady state condition (no spin involved) by the author and others, little or no studies have been conducted on spin effects. The so called Magnus effect on a sphere is well known in fluid mechanics. It is believed that the spinning can affect aerodynamic drag and lift of a tennis ball thus the motion and flight path of the ball. Therefore, the primary objectives of this work are to study the spin effects using both experimental and computational methods. In order to achieve these objectives, a series of tennis balls were used to measure their aerodynamics forces as a function of wind speeds, seam orientation and spins. The experimental study was conducted in the RMIT Industrial Wind Tunnel. A computational study of a simplified tennis ball was also studied using commercial software ‘FLUENT’. The CFD results were compared with the experimental findings. Flow around the ball was visualised with smoke

Guillain-Barré Syndrome-related campylobacter jejuni in Bangladesh: ganglioside mimicry and cross-reactive antibodies

BACKGROUND: <br/> Campylobacter jejuni is the predominant antecedent infection in Guillain-Barré syndrome (GBS). Molecular mimicry and cross-reactive immune responses to C. jejuni lipo-oligosaccharides (LOS) precipitate the development of GBS, although this mechanism has not been established in patients from developing countries. We determined the carbohydrate mimicry between C. jejuni LOS and gangliosides, and the cross-reactive antibody response in patients with GBS in Bangladesh.<br/> METHODOLOGY:<br/> Sera from 97 GBS patients, and 120 neurological and family controls were tested for antibody reactivity against LOS from C. jejuni isolates from GBS patients in Bangladesh (BD-07, BD-39, BD-10, BD-67 and BD-94) by enzyme-linked immunosorbent assay (ELISA). Cross-reactivity to LOS was determined by ELISA. The LOS outer core structures of C. jejuni strains associated with GBS/MFS were determined by mass spectrometry.<br/> PRINCIPLE FINDINGS:<br/> IgG antibodies to LOS from C. jejuni BD-07, BD-39, BD-10, and BD-67 IgG antibodies were found in serum from 56%, 58%, 14% and 15% of GBS patients respectively, as compared to very low frequency (<3%) in controls (p<0.001). Monoclonal antibodies specific for GM1 and GD1a reacted strongly with LOS from the C. jejuni strains (BD-07 and BD-39). Mass spectrometry analysis confirmed the presence of GM1 and GD1a carbohydrate mimics in the LOS from C. jejuni BD-07 and BD-39. Both BD-10 and BD-67 express the same LOS outer core, which appears to be a novel structure displaying GA2 and GD3 mimicry. Up to 90-100% of serum reactivity to gangliosides in two patients (DK-07 and DK-39) was inhibited by 50 µg/ml of LOS from the autologous C. jejuni isolates. However, patient DK-07 developed an anti-GD1a immune response while patient DK-39 developed an anti-GM1 immune response.<br/> CONCLUSION:<br/> Carbohydrate mimicry between C. jejuni LOS and gangliosides, and cross-reactive serum antibody precipitate the majority of GBS cases in Bangladesh

PET and MRI for the evaluation of regional myocardial perfusion and wall thickening after myocardial infarction

Deterioration of left ventricular (LV) function after myocardial infarction (MI) is a major cause of heart failure. Myocardial perfusion performance may play an important role in deterioration or improvement in LV function after MI. The aim of this study was to evaluate the myocardial perfusion reserve (MPR) and stress perfusion in deteriorating and non-deteriorating LV segments in patients after MI by PET and MRI, respectively. Regional wall thickening of 352 segments in 22 patients was assessed at 4 and 24 months after MI by cardiac MRI. PET was performed to evaluate MPR and adenosine stress N-13-ammonia perfusion 24 months after MI. Segments were divided into four groups according to deterioration or improvement in wall thickening. Normal functional segments at 4 months after MI that remained stable had a significantly higher mean MPR and mean stress perfusion PET value than deteriorated segments (p < 0.001). Furthermore, dysfunctional segments that improved had a significantly higher mean stress perfusion PET value than dysfunctional segments that remained dysfunctional (p < 0.001). This study demonstrated the additional value of myocardial perfusion assessment in relation to the functional integrity of the injured myocardium. Segmental functional LV improvement after MI was associated with better regional myocardial perfusion characteristics. Furthermore, the amount of wall thickening reduction was associated with regional myocardial perfusion abnormalities in patients after MI

The Impact of Curriculum Design in the Acquisition of Knowledge of Oncology: Comparison Among Four Medical Schools

Over the past 5years, cancer has replaced coronary heart disease as the leading cause of death in the Netherlands. It is thus paramount that medical doctors acquire a knowledge of cancer, since most of them will face many patients with cancer. Studies, however, have indicated that there is a deficit in knowledge of oncology among medical students, which may be due not only to the content but also to the structure of the curriculum. In this study, we compared students' knowledge acquisition in four different undergraduate medical programs. Further, we investigated possible factors that might influence students' knowledge growth as related to oncology. The participants comprised 1440 medical students distributed over four universities in the Netherlands. To measure students' knowledge of oncology, we used their progress test results from 2007 to 2013. The progress test consists of 200 multiple-choice questions; this test is taken simultaneously four times a year by all students. All questions regarding oncology were selected. We first compared the growth of knowledge of oncology using mixed models. Then, we interviewed the oncology coordinator of each university to arrive at a better insight of each curriculum. Two schools showed similar patterns of knowledge growth, with a slight decrease in the growth rate for one of them in year 6. The third school had a faster initial growth with a faster decrease over time compared to other medical schools. The fourth school showed a steep decrease in knowledge growth during years 5 and 6. The interviews showed that the two higher-scoring schools had a more focused semester on oncology, whereas in the others, oncology was scattered throughout the curriculum. Furthermore, the absence of a pre-internship training program seemed to hinder knowledge growth in one school. Our findings suggest that curricula have an influence on students' knowledge acquisition. A focused semester on oncology and a pre-internship preparatory training program are likely to have a positive impact on students' progress in terms of knowledge of oncology

Re-expansion of balloon-expandable stents after growth

AbstractObjectives. The purpose of this study was to evaluate the feasibility of re-expansion of balloon expandable intravascular stents and to examine the gross and histologic effects of re-expansion on vascular integrity.Background. Intravascular stents have been used successfully as an adjunct to balloon dilation of congenital pulmonary artery branch stenosis and postoperative stenosis of the pulmonary arteries in children. However, use of rigid stents in children could result in development of relative stenosis at the site of stent implantation with subsequent growth of the child.Methods. Stainless steel “iliac” stents were placed in the thoracic aorta of 10 normal juvenile swine by a transcatheter technique. Angiography and re-expansion were performed at a mean of 11 weeks (n = 9) and again at 18 weeks (n = 5). After euthanasia, the aortic specimens were removed for gross and histologic examination.Results. Stents were successfully implanted in 10 swine. Re-expansion was successfully performed in each animal at 11 weeks and at 18 weeks. Aortic growth produced a relative constriction of the aorta of 20% ± 10% (mean ± SD) at the site of stent implantation at both 11 and 18 weeks. Re-expansion produced a significant increase in mean stent diameter from 10.1 ± 1 mm to 12.3 ± 1.2 mm at 11 weeks and from 11.2 ± 0.7 to 13.5 ± 1.1 mm at 18 weeks after implantation (p < 0.001). Balloon dilation produced a relative increase in stent diameter of 21% ± 7% at 11 weeks and 18% ± 4% at 18 weeks. Stent re-expansion was accompanied by plastic deformation of the neointima without neointimal dissection. Where neointima was thick, there was no evidence of neointimal abrasion, but where neointima was thin, areas of localized neointimal abrasion were observed with focal fibrin and platelet adherence to the stent struts. There was no evidence of medial or adventitial hemorrhage or dissection produced by re-expansion.Conclusions. Re-expansion of intravascular stents is feasible after growth in juvenile swine without significant injury to neointima, media or adventitia. The results of this study support careful and selective use of intravascular stents as an adjunct to balloon dilation of congenital stenoses in children

Myocardial perfusion reserve compared with peripheral perfusion reserve: A [13N]ammonia PET study

INTRODUCTION: [13N]ammonia PET allows quantification of myocardial perfusion. The similarity between peripheral flow and myocardial perfusion is unclear. We compared perfusion flow in the myocardium with the upper limb during rest and adenosine stress [13N]ammonia PET to establish whether peripheral perfusion reserve (PPR) correlates with MPR. METHODS: [13N]ammonia myocardial perfusion PET-scans of 58 patients were evaluated (27 men, 31 women, age 64 ± 13 years) and were divided in four subgroups: patients with coronary artery disease (CAD, n = 15), cardiac syndrome X (SX, n = 14), idiopathic dilating cardiomyopathy (DCM, n = 16), and normal controls (NC, n = 13). Peripheral limb perfusion was measured in the muscular tissue of the proximal upper limb and quantified through a 2-tissue-compartment model and the PPR was calculated (stress/rest ratio). MPR was also calculated by a 2-tissue-compartment model. The PPR results were compared with the MPR findings. RESULTS: Mean myocardial perfusion increased significantly in all groups as evidenced by the MPR (CAD 1.99 ± 0.47; SX 1.39 ± 0.31; DCM 1.72 ± 0.69; NC 2.91 ± 0.78). Mean peripheral perfusion also increased but not significantly and accompanied with great variations within and between groups (mean PPR: CAD 1.30 ± 0.79; SX 1.36 ± 0.71; DCM 1.60 ± 1.22; NC 1.27 ± 0.63). The mean difference between PPR and MPR for all subpopulations varied widely. No significant correlations in flow reserve were found between peripheral and myocardial microcirculatory beds in any of the groups (Total group: r = -0.07, SEE = 0.70, CAD: r = 0.14, SEE = 0.48, SX: r = 0.17, SEE = 0.30, DCM: r = -0.11, SEE = 0.71, NC: r = -0.19, SEE = 0.80). CONCLUSION: No correlations between myocardial and peripheral perfusion (reserve) were found in different patient populations in the same PET session. This suggests a functional difference between peripheral and myocardial flow in the response to intravenously administered adenosine stress

Investigation into cardiac sympathetic innervation during the commencement of haemodialysis in patients with chronic kidney disease

Background: Patients with chronic kidney disease (CKD) who undergo chronic haemodialysis (HD) show altered sympathetic tone, which is related to a higher cardiovascular mortality. The purpose of this study was to investigate the effect of transition from pre-HD to HD on cardiac sympathetic innervation. Methods: Eighteen patients aged 58 ± 18 years (mean ± standard deviation [SD]), 13 males and five females, with stage 5 CKD and nine healthy control subjects aged 52 ± 17 (mean ± SD), three males and six females, were included in this prospective study between May 2010 and December 2013. All patients underwent 123I-labelled meta-iodobenzylguanidine (123I-MIBG) scintigraphy for cardiac sympathetic innervation and electrocardiographically gated adenosine stress and rest 99mTc-labelled tetrofosmin single-photon emission computed tomography for myocardial perfusion imaging prior to (pre-HD) and 6 months after the start of HD. Results of 123I-MIBG scans in patients were compared to controls. Impaired cardiac sympathetic innervation was defined as late heart-to-mediastinum ratio (HMR) < 2.0. Results: Mean late HMR was lower in patients during HD (2.3) than in controls (2.9) (p = 0.035); however, in patients it did not differ between pre-HD and after the start of HD. During HD, two patients showed new sympathetic innervation abnormalities, and in three patients innervation abnormalities seemed to coincide with myocardial perfusion abnormalities. Conclusions: CKD patients show cardiac sympathetic innervation abnormalities, which do not seem to progress during the maintenance HD. The relationship between sympathetic innervation abnormalities and myocardial perfusion abnormalities in HD patients needs further exploration