Nonionic fluorinated-hydrogenated surfactants for the design of mesoporous silica materials.

We have investigated the influence of the ratio between the volume of the hydrophilic head (VA) and the volume of the hydrophobic part (VB) of the surfactant on the mesopore ordering. To understand the difference of behavior we have performed a complete study dealing with fluorinated [Rm(F)(EO)n] and hydrogenated [Rm(H)(EO)n] surfactants. Their mixtures have also been taken into account. Here only the phase diagrams and the structural parameters of the liquid crystal phases of the mixed systems are reported. We have shown that the mutual or partial miscibility of the fluorinated and the hydrogenated surfactants depends on the number of oxyethylene units of each surfactant. To follow, various systems were used for the preparation of silica mesoporous materials via a cooperative templating mechanism (CTM). Results clearly reveal that VA/VB ratios in the range between 0.95 and 1.78 lead to the formation of well-ordered mesostructures. Wormhole-like structures are obtained for higher or lower values. Moreover, results show that from the VA/VB point of view, polyoxyethylene fluoroalkyl ether surfactants behave like their hydrogenated analogues.

Relation between the lower consolute boundary and the structure of mesoporous silica materials.

In this study, we have shed some light on the relation between the position of the lower consolute boundary of various nonionic surfactants in water and the structure of the mesoporous silica materials synthesized from these surfactants-based systems. In the first part, the lower consolute boundary was shifted by adding salts. Depending on the features of the phase diagram, we have looked for either a salting out or a salting in effect. Mesoporous materials were prepared from a micellar solution of the investigated surfactants. Results clearly evidenced that the cooperative self-assembly mechanism is not favored if the lower consolute boundary is not shifted toward high temperatures. Moreover, the higher the difference between the phase separation temperature and the temperature at which the silica precursor is added to the surfactant solution, the better the mesopore ordering is. In the second part, this tendency has been confirmed by using a hydrogenated surfactant as additive.

Design of ordered bimodal mesoporous silica materials by using a mixed fluorinated-hydrogenated surfactant-based system.

Mesoporous silica materials have been prepared using aqueous solutions of hydrogenated-fluorinated surfactant mixtures. The phase behavior of the C18H35(OC2H4)10-C6F15C2H4(OC2H4)11OH [RH18(EO)10-RF6(EO)11] mixture in aqueous solution was first established at the temperature at which the silica source is added, i.e., 20 or 40 degrees C. We have delimited the different phase domains. Concerning the mesostructured silica, whatever the temperature at which the silica source is added, mesoporous material with a hexagonal array of their channel is formed via a cooperative templating mechanism (CTM), if the content of RF6(EO)11 in the surfactant mixture is lower than 50%. Moreover, when the silica source is added at 40 degrees C, the recovered materials exhibit a bimodal pore size distribution. The appearance of this bimodality has been related to the coexistence of hydrogenated micelles with fluorinated wormlike micelles. By contrast, the bimodality is not observed when the silica source is added at 20 degrees C.

[A case of intrauterine dwarfism with enlargement of the cortex of the long bones]. / Une observation de nanisme à début intra-utérin avec élargissement de la corticale des os longs.

The case of a girl with severe, predominantly mesomelic, intrauterine dwarfism with acromicria is reported. Other anomalies included ligamentary hyperlaxity, clinodactyly of the fifth fingers, and narrow dental arches. Roentgenograms failed to disclose any metaphyseal or epiphyseal anomalies; long bones were narrow and short with thick cortices and the pelvis had an unusual appearance. This case is reminiscent of a constitutional disease with elective involvement of the cortices but distinctive features include the very early onset and the severity of statural growth failure.

[Hydrocholecystitis in children and newborn infants. Apropos of 3 cases]. / L'hydrocholécyste chez l'enfant et le nouveau-né. A propos de trois observations.

We report two cases of hydrocholecystitis in children and one in a neonate. One child had hepatitis A and the other had typhoid fever. A beta-hemolytic group B streptococcal infection was found in the neonate. In all three cases, the first manifestation was an abdominal mass and treatment of the causative disease ensured recovery. These three observations provided us with the opportunity for reviewing the literature. Isolated hydrocholecystitis is distinguished from hydrocholecystitis as a symptom. The clinical evaluation and diagnostic investigations are described in detail; special attention is given to abdominal ultrasonography. Etiology and pathophysiology, as well as management are discussed. Our three cases and the review of the literature confirm the benign prognosis of this condition.

Increased serum levels of endopeptidase 24.11 ('enkephalinase') in patients with end-stage renal failure.

Endopeptidase 24.11, a widely distributed membrane-bound peptidase is found in low levels in the serum of normal individuals. Although increased levels of the enzyme have been found in sera of patients with sarcoidosis and adult respiratory distress syndrome, the cellular origin of circulating endopeptidase 24.11 remains unknown. As the brush border of the proximal tubular epithelial cells have the highest endopeptidase specific activity, we investigated the possible contribution of the kidney to the release of endopeptidase 24.11 in the systemic circulation. Therefore, we measured serum levels of the enzyme in patients with end-stage renal failure (ESRF) treated by haemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). Increased serum levels of endopeptidase 24.11 were observed both in HD patients (mean +/- SEM: 74.6 +/- 20.9 ng/ml) and in CAPD patients (mean +/- SEM: 45.1 +/- 8.1 ng/ml) as compared to normal individuals (mean +/- SEM: 13.6 +/- 1.4 ng/ml). Endopeptidase levels remain stable during haemodialysis sessions on two different dialysis membranes. Finally, serum levels of the enzyme in anephric patients tend to be lower than in ESRF patients, suggesting that the kidney may contribute to the generation of the circulating form of endopeptidase 24.11.

Degradation of human atrial natriuretic peptide by human brain membranes.

Human atrial natriuretic peptide (Ser 99-Tyr 126) was rapidly degraded by both choroid plexus and hypothalamic membranes with a complex pattern of cleavage. The use of protease inhibitors allowed a preliminary characterization of the enzymes involved in the hydrolysis of the Ser-Phe and Phe-Arg bonds of iodine-labelled atrial natriuretic peptide. The C-terminal tripeptide was generated by three different enzymatic activities acting on the Ser-Phe bond: endopeptidase 24.11, a phosphoramidon-insensitive metallopeptidase and a thiol protease. Peptides like substance P, neurotensin, bradykinin inhibited the cleavage of the Ser-Phe bond of atrial natriuretic peptide. The C-terminal tripeptide was further degraded by aminopeptidases. Cleavage of the C-terminal dipeptide was inhibited by aprotinin, suggesting the contribution of brain kallikrein in the formation of this metabolite. These results show that many different proteases were involved in the hydrolysis of the C-terminal sequence of atrial natriuretic peptide, at least in vitro and underline the complexity of neuropeptide catabolism by brain preparations.

[Echographic aspects of intestinal invagination]. / Aspects échographiques de l'invagination intestinale.

Two cases of intestinal invagination were investigated by ultrasonography. The image in the first case was related to the palpable abdominal mass, suggesting a digestive tract lesion. In the second case, direct visualization of the invaginated but in the intestinal lamen appears to be a specific image which has not been reported previously.