Study on the bmi status of secondary school children in the south-eastern part of Romania

The study is based on the body mass index of students between the ages of 10 and 14. The body mass index of5043 students was tested in order to bring out the fact that the degree of obesity is not as high as health representatives claim. By means of this research we found that a percentage of 49% of the tested children were normal weight and only 2.31% were obese. The causes of obesity in these subjects may be metabolic disorders. The existence of obesity cannot be attributed only to eating habits, lack of physical activity or a sedentary lifestyle

Modification of Experimental Protocols for a Space Shuttle Flight and Applications for the Analysis of Cytoskeletal Structures During Fertilization, Cell Division , and Development in Sea Urchin Embryos

To explore the role of microgravity on cytoskeletal organization and skeletal calcium deposition during fertilization, cell division, and early development, the sea urchin was chosen as a model developmental system. Methods were developed to employ light, immunofluorescence, and electron microscopy on cultures being prepared for flight on the Space Shuttle. For analysis of microfilaments, microtubules, centrosomes, and calcium-requiring events, our standard laboratory protocols had to be modified substantially for experimentation on the Space Shuttle. All manipulations were carried out in a closed culture chamber containing 35 ml artificial sea water as a culture fluid. Unfertilized eggs stored for 24 hours in these chambers were fertilized with sperm diluted in sea water and fixed with concentrated fixatives for final fixation in formaldehyde, taxol, EGTA, and MgCl2(exp -6)H2O for 1 cell to 16 cell stages to preserve cytoskeletal structures for simultaneous analysis with light, immunofluorescence, and electron microscopy, and 1.5 percent glutaraldehyde and 0.4 percent formaldehyde for blastula and plueus stages. The fixed samples wre maintained in chambers without degradation for up to two weeks after which the specimens were processed and analyzed with routine methods. Since complex manipulations are not possible in the closed chambers, the fertilization coat was removed from fixation using 0.5 percent freshly prepared sodium thioglycolate solution at pH 10.0 which provided reliable immunofluorescence staining for microtubules. Sperm/egg fusion, mitosis, cytokinesis, and calcium deposition during spicule formatin in early embryogenesis were found to be without artificial alterations when compared to cells fixed fresh and processed with conventional methods

X-Ray Microanalysis of Calcium Containing Organelles in Resin Embedded Tissue

The localization of calcium in cell organelles at the electron microscope level is often achieved through cytochemical techniques, and verified by X-ray microanalysis. Various methods have been used to cytochemically detect calcium or calcium-binding sites : calcium loading, calcium substitution by strontium, barium, or even lead, and calcium precipitation by oxalate, phosphate, fluoride, or pyroantimonate. Their results may have heuristic value, particularly in preliminary studies of poorly known cell types. A complementary and more physiological approach is offered by quantitative measurement of the total calcium content of organelles after cryofixation. Resin embedding is less demanding than cryomicrotomy and gives better images : it can be used after cryosubstitution in the presence of oxalic acid. This technique was tested, and applied to several cell types

Effects of Ionomycin on Egg Activation and Early Development in Starfish

Ionomycin is a Ca2+-selective ionophore that is widely used to increase intracellular Ca2+ levels in cell biology laboratories. It is also occasionally used to activate eggs in the clinics practicing in vitro fertilization. However, neither the precise molecular action of ionomycin nor its secondary effects on the eggs' structure and function is well known. In this communication we have studied the effects of ionomycin on starfish oocytes and zygotes. By use of confocal microscopy, calcium imaging, as well as light and transmission electron microscopy, we have demonstrated that immature oocytes exposed to ionomycin instantly increase intracellular Ca2+ levels and undergo structural changes in the cortex. Surprisingly, when microinjected into the cells, ionomycin produced no Ca2+ increase. The ionomycin-induced Ca2+ rise was followed by fast alteration of the actin cytoskeleton displaying conspicuous depolymerization at the oocyte surface and in microvilli with concomitant polymerization in the cytoplasm. In addition, cortical granules were disrupted or fused with white vesicles few minutes after the addition of ionomycin. These structural changes prevented cortical maturation of the eggs despite the normal progression of nuclear envelope breakdown. At fertilization, the ionomycin-pretreated eggs displayed reduced Ca2+ response, no elevation of the fertilization envelope, and the lack of orderly centripetal translocation of actin fibers. These alterations led to difficulties in cell cleavage in the monospermic zygotes and eventually to a higher rate of abnormal development. In conclusion, ionomycin has various deleterious impacts on egg activation and the subsequent embryonic development in starfish. Although direct comparison is difficult to make between our findings and the use of the ionophore in the in vitro fertilization clinics, our results call for more defining investigations on the issue of a potential risk in artificial egg activation

Frottement de films minces d'hydrogel : poroélasticité et interface

Thin hydrogel films find applications in biomedical engineering (synthetic articular cartilage, contact lenses) or optics (anti-fog coatings) thanks to their biocompatibility, transparency, and lubricating properties. The frictional properties of these systems in water, which are crucial for their use, arise from the complex coupling of several physical mechanisms. Fluid film lubrication, poroelastic flows in the gel due to pressure gradients, and molecular interactions at the interface between the gel and the sliding surface are all involved in gel friction.In the present work, we provide a description of the role played by interfacial molecular interactions on friction of hydrogels in water. To this end, we built an experimental set up in which both poroelastic flows and water film lubrication are suppressed. By sliding a spherical silica lens with a rotative trajectory over a micrometer-thick polydimethylacrylamide gel film immersed in water, under imposed normal force and velocity, we measure the frictional forces and observe the gel/silica contact by interferometry. By functionalizing the silica with various silanes, we show an effect of surface chemistry of the silica lens on the measured friction forces and their dependence on sliding speed, over three decades in velocity. In transient regime, we demonstrate an ageing phenomenon of the interface when the lens is maintained in contact with the gel over long times before sliding initiation. We derive a model for steady state friction based on the thermodynamic adsorption/desorption of polymer chains on the sliding surface. This model successfully accounts for our experimental observations with a set of molecular parameters which agree with the physico-chemistry of our silanated systems.Les films minces d’hydrogel sont des systèmes prometteurs pour des applications en ingénierie biomédicale (cartilage articulaire synthétique, lentilles de contact) ou optique (revêtements anti-buée) grâce à leur biocompatibilité, leur transparence et leurs propriétés lubrifiantes. Les propriétés frictionnelles de ces systèmes dans l’eau, cruciales pour leur utilisation, sont complexes car elles mettent en jeu plusieurs mécanismes physiques souvent couplés. La lubrification par un film d’eau, les écoulements poroélastiques dans le gel sous l’effet de gradients de pression et les interactions moléculaires à l’interface entre le gel et la surface glissante sont évoqués pour expliquer le frottement des gels.Dans ce travail de thèse, nous avons mesuré puis décrit le rôle des interactions moléculaires interfaciales dans le frottement des hydrogels dans l’eau. Pour cela, nous avons développé un dispositif expérimental permettant de supprimer à la fois les contributions poroélastiques et de lubrification par un film d’eau. En faisant glisser une lentille sphérique de silice en rotation sur un film de gel de polydiméthylacrylamide d’épaisseur micrométrique immergé dans l’eau, sous force normale et vitesse imposées, nous mesurons les forces de frottement et nous observons le contact gel/silice par interférométrie. En fonctionnalisant la silice par des silanes variés, nous mettons en évidence un effet important de la chimie de surface de la lentille de silice sur les forces de frottement mesurées et leur dépendance en vitesse de glissement, laquelle est variée sur trois ordres de grandeur. En régime transitoire, nous mettons en évidence un phénomène de vieillissement de l’interface lorsque la lentille est maintenue en contact avec le gel sur des temps longs avant d’initier le glissement. Pour discuter ces observations, nous proposons un modèle de frottement en régime stationnaire basé sur l’adsorption/désorption thermodynamique des chaînes polymères sur la surface glissante. Ce modèle rend compte des observations expérimentales à partir de paramètres moléculaires en accord avec la physicochimie des silices silanisées

Friction of thin hydrogel films : poroelasticity and interface

Les films minces d’hydrogel sont des systèmes prometteurs pour des applications en ingénierie biomédicale (cartilage articulaire synthétique, lentilles de contact) ou optique (revêtements anti-buée) grâce à leur biocompatibilité, leur transparence et leurs propriétés lubrifiantes. Les propriétés frictionnelles de ces systèmes dans l’eau, cruciales pour leur utilisation, sont complexes car elles mettent en jeu plusieurs mécanismes physiques souvent couplés. La lubrification par un film d’eau, les écoulements poroélastiques dans le gel sous l’effet de gradients de pression et les interactions moléculaires à l’interface entre le gel et la surface glissante sont évoqués pour expliquer le frottement des gels.Dans ce travail de thèse, nous avons mesuré puis décrit le rôle des interactions moléculaires interfaciales dans le frottement des hydrogels dans l’eau. Pour cela, nous avons développé un dispositif expérimental permettant de supprimer à la fois les contributions poroélastiques et de lubrification par un film d’eau. En faisant glisser une lentille sphérique de silice en rotation sur un film de gel de polydiméthylacrylamide d’épaisseur micrométrique immergé dans l’eau, sous force normale et vitesse imposées, nous mesurons les forces de frottement et nous observons le contact gel/silice par interférométrie. En fonctionnalisant la silice par des silanes variés, nous mettons en évidence un effet important de la chimie de surface de la lentille de silice sur les forces de frottement mesurées et leur dépendance en vitesse de glissement, laquelle est variée sur trois ordres de grandeur. En régime transitoire, nous mettons en évidence un phénomène de vieillissement de l’interface lorsque la lentille est maintenue en contact avec le gel sur des temps longs avant d’initier le glissement. Pour discuter ces observations, nous proposons un modèle de frottement en régime stationnaire basé sur l’adsorption/désorption thermodynamique des chaînes polymères sur la surface glissante. Ce modèle rend compte des observations expérimentales à partir de paramètres moléculaires en accord avec la physicochimie des silices silanisées.Thin hydrogel films find applications in biomedical engineering (synthetic articular cartilage, contact lenses) or optics (anti-fog coatings) thanks to their biocompatibility, transparency, and lubricating properties. The frictional properties of these systems in water, which are crucial for their use, arise from the complex coupling of several physical mechanisms. Fluid film lubrication, poroelastic flows in the gel due to pressure gradients, and molecular interactions at the interface between the gel and the sliding surface are all involved in gel friction.In the present work, we provide a description of the role played by interfacial molecular interactions on friction of hydrogels in water. To this end, we built an experimental set up in which both poroelastic flows and water film lubrication are suppressed. By sliding a spherical silica lens with a rotative trajectory over a micrometer-thick polydimethylacrylamide gel film immersed in water, under imposed normal force and velocity, we measure the frictional forces and observe the gel/silica contact by interferometry. By functionalizing the silica with various silanes, we show an effect of surface chemistry of the silica lens on the measured friction forces and their dependence on sliding speed, over three decades in velocity. In transient regime, we demonstrate an ageing phenomenon of the interface when the lens is maintained in contact with the gel over long times before sliding initiation. We derive a model for steady state friction based on the thermodynamic adsorption/desorption of polymer chains on the sliding surface. This model successfully accounts for our experimental observations with a set of molecular parameters which agree with the physico-chemistry of our silanated systems