Instituto Superior Técnico

About: Instituto Superior Técnico is a based out in . It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 10085 authors who have published 30226 publications receiving 667524 citations. The organization is also known as: IST & Instituto Superior Tecnico.

Expansion of mouse embryonic stem cells on microcarriers

Abstract: Embryonic stem (ES) cells have been shown to differentiate in vitro into a wide variety of cell types having significant potential for tissue regeneration. Therefore, the operational conditions for the ex vivo expansion and differentiation should be optimized for large-scale cultures. The expansion of mouse ES cells has been evaluated in static culture. However, in this system, culture parameters are difficult to monitor and scaling-up becomes time consuming. The use of stirred bioreactors facilitates the expansion of cells under controlled conditions but, for anchorage-dependent cells, a proper support is necessary. Cytodex-3, a microporous microcarrier made up of a dextran matrix with a collagen layer at the surface, was tested for its ability to support the expansion of the mouse S25 ES cell line in spinner flasks. The effect of inocula and microcarrier concentration on cell growth and metabolism were analyzed. Typically, after seeding, the cells exhibited a growth curve consisting of a short death or lag phase followed by an exponential phase leading to the maximum cell density of 2.5-3.9 x 10(6) cells/mL. Improved expansion was achieved using an inoculum of 5 x 10(4) cells/mL and a microcarrier concentration of 0.5 mg/mL. Medium replacement allowed the supply of the nutrients and the removal of waste products inhibiting cell growth, leading to the maintenance of the cultures in steady state for several days. These conditions favored the preservation of the S25 cells pluripotent state, as assessed by quantitative real-time PCR and immunostaining analysis.

Metal complexes of cyclen and cyclam derivatives useful for medical applications: a discussion based on thermodynamic stability constants and structural data

Abstract: A series of the most common chelators used in magnetic resonance imaging (MRI) and in radiopharmaceuticals for medical diagnosis and tumour therapy, H4dota, H4teta, H8dotp and H8tetp, is examined from a chemical point of view. Differences between 12- and 14-membered tetraazamacrocyclic derivatives with methylcarboxylate and methylphosphonate pendant arms and their chelates with divalent first-series transition metal and trivalent lanthanide ions are discussed on the basis of their thermodynamic stability constants, X-ray structures and theoretical studies.

Lycopene and β-Carotene Extraction from Tomato Processing Waste Using Supercritical CO2

Abstract: Tomato skins and their mixtures with seeds were submitted to supercritical CO2 extraction using a flow apparatus at pressures of 250 and 300 bar and temperatures of 60 and 80 °C Two different mean particle sizes (80 and 345 μm) were used at two solvent flow rates (0792 and 135 kg/h) The yields of lipids, lycopene, and β-carotene obtained by supercritical fluid extraction were compared with those obtained by conventional organic solvent extraction Supercritical fluid extraction from tomato skins at 300 bar and 80 °C allowed the recovery of 80% of the lycopene and 88% of the β-carotene, using about 130 g of CO2 per gram of matrix at the lower flow rate of CO2

Early glycoprotein IIb–IIIa inhibitors in primary angioplasty (EGYPT) cooperation: an individual patient data meta-analysis

Abstract: Background: Even though time-to-treatment has been shown to be a determinant of mortality in primary angioplasty, the potential benefits from early pharmacological reperfusion by glycoprotein (Gp) IIb–IIIa inhibitors are still unclear. The aim of this meta-analysis was to combine individual data from all randomised trials conducted on facilitated primary angioplasty by the use of early Gp IIb–IIIa inhibitors. Methods and results: The literature was scanned by formal searches of electronic databases (MEDLINE, EMBASE) from January 1990 to October 2007. All randomised trials on facilitation by the early administration of Gp IIb–IIIa inhibitors in ST-segment elevation myocardial infarction (STEMI) were examined. No language restrictions were enforced. Individual patient data were obtained from 11 out of 13 trials, including 1662 patients (840 patients (50.5%) randomly assigned to early and 822 patients (49.5%) to late Gp IIb–IIIa inhibitor administration). Preprocedural Thrombolysis in Myocardial Infarction Study (TIMI) grade 3 flow was more frequent with early Gp IIb–IIIa inhibitors. Postprocedural TIMI 3 flow and myocardial blush grade 3 were higher with early Gp IIb– IIIa inhibitors but did not reach statistical significance except for abciximab, whereas the rate of complete STsegment resolution was significantly higher with early Gp IIb–IIIa inhibitors. Mortality was not significantly different between groups, although early abciximab demonstrated improved survival compared with late administration, even after adjustment for clinical and angiographic confounding factors. Conclusions: This meta-analysis shows that pharmacological facilitation with the early administration of Gp IIb– IIIa inhibitors in patients undergoing primary angioplasty for STEMI is associated with significant benefits in terms of preprocedural epicardial recanalisation and ST-segment resolution, which translated into non-significant mortality benefits except for abciximab.

Geometry of contact transformations and domains: orderability versus squeezing

Abstract: Gromov’s famous non-squeezing theorem (1985) states that the standard symplectic ball cannot be symplectically squeezed into any cylinder of smaller radius. Does there exist an analogue of this result in contact geometry? Our main finding is that the answer depends on the sizes of the domains in question: We establish contact nonsqueezing on large scales, and show that it disappears on small scales. The algebraic counterpart of the (non)-squeezing problem for contact domains is the question of existence of a natural partial order on the universal cover of the contactomorphisms group of a contact manifold. In contrast to our earlier beliefs, we show that the answer to this question is very sensitive to the topology of the manifold. For instance, we prove that the standard contact sphere is non-orderable while the real projective space is known to be orderable. Our methods include a new embedding technique in contact geometry as well as a generalized Floer homology theory which contains both cylindrical contact homology and Hamiltonian Floer homology. We discuss links to a number of miscellaneous topics such as topology of free loops spaces, quantum mechanics and semigroups.