Thermodynamic stability and osmotic sensitivity of small unilamellar phosphatidylcholine vesicles.

Evidence is presented to show that small unilamellar phosphatidylcholine vesicles with a diameter of approx. 20 nm are osmotically sensitive. Such vesicles respond to osmotic pressure by swelling or shrinking depending on the direction of the applied salt gradient. This is true for small unilamellar vesicles of egg phosphatidylcholine and dimyristoylphosphatidylcholine below and above their crystal-to-liquid crystal transition temperature. At the transition temperature the vesicles are osmotically insensitive due to the increased bilayer permeability resulting in rapid dissipation of salt gradients. Positive salt gradients produce shrinking and collapse of spherical phospholipid vesicles to disks. Shrinking of vesicles is associated with H2O and solute efflux, but only limited solute influx. Clustering of lipid molecules in the bilayers of the resulting disks can be detected by EPR spin labeling. Negative salt gradients produce swelling of vesicles which is associated with H2O and solute influx. Our experiments are consistent with an osmotically perturbed bilayer. In the presence of osmotic gradients the influx and efflux of H2O is coupled with the movement of ions and small molecules which in the absence of salt gradients or osmotic stress cannot pass the phospholipid bilayer. However, during osmotically induced shrinking and swelling of SUV the integrity of the phospholipid bilayer is maintained to the extent that vesicles do not break, and therefore equilibration between external medium and vesicle cavity does not take place.

[Infant feeding until the age of 4 months old in Seine-Maritime]. / L'alimentation du nourrisson jusqu'à 4 mois en Seine-Maritime.

This study reports infant feeding practices during the first 4 months of life. A representative sample of 10% of the births in the Seine-Maritime department formed the subject of a questionnaire cohort study carried on at home by public health institution for infants specialized nurses. Among 1,407 interviewed mothers, 52% had been thinking about their future child feeding before birth, essentially with their circles, especially their husbands. The type of feeding had been chosen before pregnancy in 64.3% of cases. Earlier choices resulted more often in breast-feeding. 46.2% of mothers tried to breast-feed their children, however 17% among them discontinued when back home. Carrying out breast-feeding (median duration 10 weeks) delayed the feeding diversification and was associated with a lower frequency of health difficulties in children.

[Behavior and opinions of health care personnel with regard to breast feeding]. / Comportements et opinions du personnel soignant à l'égard de l'allaitement maternel.

Breast feeding (BF) practice is related to cultural, social and economic patterns of the future mothers; nevertheless hospital personnel seems to have some influence on infant feeding habits. This study describes the professional practices among personnel in the maternity hospitals of the Departement de la Seine Maritime (France) and reports their opinions about BF. Most of the respondents consider that they have a small role in influencing the decision to breast feed, the choice being made before pregnancy. Delivery training sessions seem to be the most suitable time for information about BF. Psychological arguments are considered as the most effective approach. BF is not estimated as leading to an increased work goal by hospital personnel. BF appears to be generally well controlled by mothers before discharge. Technical factors were given as the primary influencing reason for cessation of BF. This survey indicates several ways for establishing future health education programs for the promotion of BF.