Polystyrènes à motifs bifonctionnels: synthèses,caractérisations et modifications chimiques

Four enol esters with a styrene skeleton ( 3a – d ) were synthesized in two steps from commercial products and polymerized or copolymerized with styrene as a comonomer. The polymers and copolymers ( 7 and 8 ) were characterized. They are stable up to 140°C and lose acetic acid upon heating. Chemical modifications, such as nucleophilic substitutions with cyanide ions or nucleophilic addition of butyllithium, were studied.     

Spectral methods in machine learning and new strategies for very large datasets

Spectral methods are of fundamental importance in statistics and machine learning, because they underlie algorithms from classical principal components analysis to more recent approaches that exploit manifold structure. In most cases, the core technical problem can be reduced to computing a low-rank approximation to a positive-definite kernel. For the growing number of applications dealing with very large or high-dimensional datasets, however, the optimal approximation afforded by an exact spectral decomposition is too costly, because its complexity scales as the cube of either the number of training examples or their dimensionality. Motivated by such applications, we present here 2 new algorithms for the approximation of positive-semidefinite kernels, together with error bounds that improve on results in the literature. We approach this problem by seeking to determine, in an efficient manner, the most informative subset of our data relative to the kernel approximation task at hand. This leads to two new strategies based on the Nyström method that are directly applicable to massive datasets. The first of these—based on sampling—leads to a randomized algorithm whereupon the kernel induces a probability distribution on its set of partitions, whereas the latter approach—based on sorting—provides for the selection of a partition in a deterministic way. We detail their numerical implementation and provide simulation results for a variety of representative problems in statistical data analysis, each of which demonstrates the improved performance of our approach relative to existing methods.     

Molecular detection of human papillomavirus in 594 uterine cervix samples from Moroccan women (147 biopsies and 447 swabs).

Uterine cervix cancer is the second most frequent female cancer after breast cancer in Morocco and represents a public health problem. Cervical cancer is highly linked to human papillomavirus (HPV) especially types 16 and 18 which are the highly oncogenic genotypes. To identify the contribution of HPV testing in the prevention of cervical cancer in Morocco, 147 biopsies collected at the Institut National d'Oncologie and 447 swabs from pathology laboratories and gynaecologist offices in Rabat were HPV analysed. HPV testing were made without any presumption of the histopathological diagnosis. A total of 147 paraffin-embedded biopsies and 447 exfoliated cervical samples were included. Based on histopathology results of the 147 biopsies, most cervical lesions were invasive carcinomas and non specific inflammations (NSI). With the molecular assay, HPV was detected in 91/147 (62%) patients. The high risk types 16 and 18 were found in 45% of the cases (41/91) and HPV 18 in 19% of the cases (17/91). Double infection with HPV 16 and 18 was found in 3 cases. Among the 447 swabs tested, 28 were HPV positives. Cytology results showed that 46% were inflammations (13/28). Among them, 10 patients had a NSI and only 3 patients had a cytology diagnosis of HPV infection. Based on these data, HPV testing should be associated to cervical cytology screening according to two algorithms established in function of the age of the patient and viral natural history. Combination of cytology and HPV testing allow identification of patient with high risk for development of high grade cervical lesions and improve cervical cancer prevention.     

Ochratoxin A in human plasma in Morocco: a preliminary survey

Available epidemiological information seems to indicate that Balkan endemic nephropathy is associated with consumption patterns involving foodstuffs contaminated with ochratoxin A (OTA) and with a higher frequency of OTA-positive blood samples. The aim of this preliminary study was to assess OTA concentrations in human plasma in Morocco. Therefore, samples from 309 healthy volunteers (213 males, 96 females) were analysed. The analyses revealed that 60% of the human plasma sampled was positive for OTA (61.5% in the male and 56% in the female population), and an average concentration of 0.29 ng/mL (0.31 ng/mL in males, 0.26 ng/mL in females). The highest concentration found was 6.59 ng/mL. The results suggest that the Moroccan population is exposed to OTA, even though the OTA plasma levels are lower than that reported in some North African countries.     

Cardiac and vascular hypertrophy in hypertension due to angiotensin II. Effect of losartan and bosentan

We assessed the role of angiotensin (Ang) II type 1 receptor (AT1) and endothelin type A and B (ETA & ETB) receptor in cardiovascular hypertrophy associated with angiotensin II-induced hypertension (200 ng/kg.min s.c. for 10 or 17 days). Antagonism of AT1 receptors was obtained by oral administration of losartan (10 or 30 mg/kg.day) and blockade of ETA and ETB receptors was obtained by oral administration of bosentan (30 mg/kg.day). Losartan and bosentan were administered 24 h before and during the 10 days of angiotensin II (prevention) or they were given after the development of hypertension i.e. from day 10 to 17 of angiotensin II (treatment). Tail-cuff pressure (TCP) was measured before and at the end of the period of administration of antagonists. At the end of experiments, cross sectional area (CSA, mm2) of the carotid was measured after perfusion and fixation at 100 mmHg and heart weight index (HWI, mg/g body weight) was determined. Results are mean +/- SEM. [table: see text] In addition to its blood pressure lowering effect, both doses of losartan prevented and reversed the cardiovascular hypertrophy induced by angiotensin II. Similarly, bosentan prevented and reversed the effect of angiotensin II on cardiovascular structure independently of arterial pressure. These results indicate that the effect of angiotensin II on blood pressure, heart and carotid structure is exclusively mediated by AT1 receptors. The influence of bosentan suggests that endothelin plays an important role in local action of angiotensin II independently of blood pressure level.     

Human papillomavirus DNA in cervical lesions from Morocco and its implications for cancer control

To determine the types of human papillomaviruses (HPV) in northern Morocco, information which is needed for the design and use of HPV vaccines, we have analysed 129 cervical biopsies from this region. In our study, 91 cases were HPV positive, 45 cases had HPV-16 DNA, and 20 cases had HPV-18 DNA. This distribution of virus type was similar in inflammatory cervical lesions and in invasive cervical carcinomas. In conclusion, the HPV type distribution in Morocco is similar to that in other African Mediterranean countries, where the proportion of HPV-18 cases is significantly higher than in Europe. Determination of virus-type distribution is essential for vaccination programs.     

Sodium ion inhibits angiogenesis of cultured rat aortic and coronary rings

High sodium intake is associated with the development of cardiac hypertrophy in man and rats independently of the rise of blood pressure. In addition, the reduced capillary density observed in striated muscle of rats fed a high salt diet suggests that angiogenesis is altered. The aim of the present experiments was to investigate the angiogenic capacities of vascular rings isolated from the aorta and the coronary artery of rats. Vascular rings (external diameter of 1 669 +/- 9 and 323 +/- 26 microm for aorta and coronary artery. respectively) are cultured in a three-dimensional collagen type I lattice and a standard medium (DMEM+HAMF12) containing 152 mM of sodium. Sodium ion associated with chloride or citrate is added to the standard medium to achieve a final concentration of sodium of 160 and 176 mM. The role of sodium-proton exchanger is evaluated through the addition of amiloride to the culture medium. Sprouts formed from vascular explants are counted every second day until days 8 to 10. Kinetics of new vessels formation and the number of sprouts were similar in aortic and coronary rings (83 +/- 5 and 95 +/- 5 sprouts, respectively). Elevation of sodium chloride concentration inhibits by 50 to 80% the neo-vessels formation in both the aorta and the coronary artery. Anti-angiogenic effect of the high sodium medium was not affected when citrate was substituted to chloride. Amiloride (3.10(-5) M) reduced the number of sprouts formed in the standard medium; however, it counteracted the anti-angiogenic effect of elevated sodium concentration. These results indicate that high extracellular concentration of sodium and not chloride anion is accompanied by a deleterious effect on angiogenic capacities of cultured aortic and coronary artery rings through modifications of trans-membrane sodium exchanges.