Tensions superficielles de copolymères méthacryliques perfluoroalkylés

The surface properties of methacrylic copolymers with a random distribution of perfluoroalkyl pendent groups were studied by a tensiometric method and were found to depend on the concentration of fluorinated units (2-hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononyl methacrylate ( 1 )), and the nature of the non-fluorinated methacrylic ester (methyl, butyl, stearyl). The surface tensions estimated by various approaches (critical surface tension, geometric and harmonic mean approximations) are very low (11 mN · m^?1 < y < 12 mN · m^?1). The surface tension of the copolymers drops drastically when a few percent of fluorinated units are incorporated into the polymeric chain. The wetting hysteresis, observed particularly in the case of water, could be due to the mobility of macromolecular chains at the interface, leading to a reorganization of fluorinated groups in order to minimize the interfacial energy.     

Isolated azygos continuation of the inferior vena cava.

Our case of azygos continuation of the inferior vena cava is very rare because there was no associated heart disease or abdominal situs inversus. The diagnosis of this anomaly of the inferior vena cava should be suspected by observation of a dilated azygos vein on the chest roentgenogram and confirmed by venography.     

Teaching personal awareness

Educators rarely consider the attitudes that determine whether a learner will use the clinical skills we teach. Nevertheless, many learners and practitioners exhibit negative attitudes that can impede the use of patient-centered skills, leading to an isolated focus upon disease and impairing the provider-patient relationship. The problem is compounded because these attitudes often are incompletely recognized by learners and therefore are difficult to change without help. We present a research-based method for teaching personal awareness of unrecognized and often harmful attitudes. We propose that primary care clinicians without mental health training can follow this method to teach students, residents, faculty, and practitioners. Such teachers/mentors need to possess an abiding interest in the personal dimension, patience with a slowly evolving process of awareness, and the ability to establish strong, ongoing relationships with learners. Personal awareness teaching may occur during instruction in basic interviewing skills but works best if systematically incorporated throughout training.     

Recycling Frank: Spontaneous emergence of homochirality in noncatalytic systems

In this work, we introduce a prebiotically relevant protometabolic pattern corresponding to an engine of deracemization by using an external energy source. The spontaneous formation of a nonracemic mixture of chiral compounds can be observed in out-of-equilibrium systems via a symmetry-breaking phenomenon. This observation is possible thanks to chirally selective autocatalytic reactions (Frank's model) [Frank, F. C. (1953) Biochim. Biophys. Acta 11, 459-463]. We show that the use of a Frank-like model in a recycled system composed of reversible chemical reactions, rather than the classical irreversible system, allows for the emergence of a synergetic autoinduction from simple reactions, without any autocatalytic or even catalytic reaction. This model is described as a theoretical framework, based on the stereoselective reactivity of preexisting chiral monomeric building blocks (polymerization, epimerization, and depolymerization) maintained out of equilibrium by a continuous energy income, via an activation reaction. It permits the self-conversion of all monomeric subunits into a single chiral configuration. Real prebiotic systems of amino acid derivatives can be described on this basis. They are shown to be able to spontaneously reach a stable nonracemic state in a few centuries. In such systems, the presence of epimerization reactions is no more destructive, but in contrast is the central driving force of the unstabilization of the racemic state.     

Inhibition of fibroblast growth factor/fibroblast growth factor receptor activity in glioma cells impedes tumor growth by both angiogenesis-dependent and -independent mechanisms

We undertook a series of systematic studies to address the role of fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) activity in tumor growth and angiogenesis. We expressed dominant-negative FGFR2 (FGFR2-DN) or FGFR1 (FGFR1-DN) in glioma C6 cells by using constitutive or tetracycline-regulated expression systems. Anchorage-dependent or independent growth was inhibited in FGFR-DN-expressing cells. Tumor development after xenografting FGFR-DN-expressing cells in immunodeficient mice or after transplantation in rat brain was strongly inhibited. Quantification of microvessels demonstrated a significant decrease in vessel density in tumors derived from FGFR-DN-expressing cells. Furthermore, in a rabbit corneal assay, the angiogenic response after implantation of FGFR-DN-expressing cells was decreased. In tumors expressing FGFR-DN, vascular endothelial growth factor expression was strongly inhibited as compared with control tumor. These results indicate that inhibition of FGF activity may constitute a dominant therapeutic strategy in the treatment of FGF-producing cerebral malignancies and may disrupt both angiogenesis-dependent and -independent signals required for glioma growth and invasion.     

Arachidonic acid protection of rat mucosa against stress ulceration

To evaluate the effect of arachidonic acid (AA), a prostaglandin precursor, on the mucosal level of PGE2 and its possible protective role against stress ulcerations, 40 Holtzman rats were divided into four groups: Group I intragastrically receiving 1 ml of normal saline (NS); Group II, NS pretreatment followed by stress; Group III, intragastric AA pretreatment without stress; and Group IV, intragastric AA followed by stress. AA was administered as a 120 mM solution in a nonionic detergent, adjusted to a pH of 8.0. Stress was provided by the cold-restraint method. After sacrifice, the number of gastric mucosal ulcerations were counted. Specimens of nonulcerated mucosa were assayed for PGE2 by derivatization with panacyl bromide and by using high-performance liquid chromatography. The animals in Groups I, III, and IV developed no gastric ulcerations and their mucosal prostaglandin E2 remained at a normal level, while those in Group II had a significant reduction of mucosal PGE2 (P less than 0.05) and a significantly increased number of gastric ulcerations (P less than 0.002). These data indicate that stress-induced mucosal ulcerations are associated with significant decreases in the gastric mucosal levels of PGE2. Intragastric administration of arachidonic acid prevents the formation of stress mucosal ulcerations and maintains a normal level of mucosal PGE2.     

Prevention of stress-induced erosive gastritis by parenteral administration of arachidonic acid

Stress-induced mucosal ulcerations are associated with a decreased synthesis of mucosal prostaglandin (PG) E2. This phenomenon is poorly understood. To investigate whether it is due to a decreased availability of the necessary substrates to the mucosa, four groups of 10 Holtzman rats were studied: group 1 received normal saline by intraperitoneal (ip) injection; group 2 also received ip normal saline, then were submitted to stress, by the cold restraint method; group 3 received a solution of arachidonic acid (AA) ip; and group 4 also received ip AA, then were submitted to stress. After sacrifice, the number of gastric ulcerations were counted and specimens of nonulcerated mucosa were assayed for PGE2 by high-performance liquid chromatography; the mean numbers of ulcers were 0, 5.8, 0.8, and 3 and the mean levels of PGE2 were 55, 41, 125, and 62 pg/mg of wet tissue for groups 1, 2, 3, and 4, respectively. It is concluded that parenteral administration of AA reduces but does not completely eliminate stress-induced gastric ulcerations and that the stressed animals synthesized half as much PGE2 as the nonstressed ones after ip administration of equal amounts of AA, suggesting that stress reduces the availability of AA to the gastric mucosa, possibly by vascular spasm.     

Inhibition of FGF receptor activity in glioma implanted into the mouse brain using the tetracyclin-regulated expression system

We have investigated growth and vascularization of malignant glioma in mice upon conditional inhibition of fibroblast growth factor (FGF) receptor activity. C6 rat glioma cells were transfected with a dominant-negative fibroblast growth factor receptor-2 (FGFR2-DN) cDNA under the control of a tetracycline-regulated expression promoter (tet off) and implanted in the brain of immunodeficient mice. Magnetic resonance imaging analysis showed a significant decrease in tumor growth 14 days after implantation when FGFR2-DN was expressed compared to control. This size difference disappeared after 20 days. However, after 20 days, tumor and endothelial cells apoptosis were higher in the FGFR2-DN group and consequently angiogenesis was decreased whereas tumor cells were similarly associated with blood vessels at the tumor periphery. Pericyte coverage was not different between the two groups but a higher amount of pericytes not associated with vessels was found in the FGFR2-DN expressing group. This demonstrates, that conditional expression of inhibitor of FGF receptor activity in gliomas implanted in the brain of immunodeficient mice can be achieved efficiently, and that FGFs are major players in glioma development and in glioma angiogenesis.