Synthesis of a polymer skeleton at the inner leaflet of liposomal membranes: polymerization of membrane-adsorbed pH-sensitive monomers

We describe the synthesis of liposomes with an artificial membrane skeleton as a model of the native cellular cytoskeleton. Similar to natural conditions, a flat polymer network is coupled to the inner membrane leaflet like a suspended ceiling via membrane-inserted anchor monomers with a spacer. The polymer is composed of DMAPMA (N-(3-N,N-dimethylaminopropyl) methacrylamide) and TEGDM (tetraethylene glycol dimethacrylate) as a linker and is coupled to the membrane anchor DOGM (1,2-distearyl-3-octaethylene glycol glycerol ether methacrylate). In the first step of the synthesis, DMAPMA and TEGDM are encapsulated into liposomes composed of egg phosphatidylcholine (EPC), and free monomers are removed by gel chromatography. At pH 10, DMAPMA adsorbs to the inner membrane surface, as demonstrated in parallel studies with lipid monolayers using a Langmuir film balance. The polymerization by UV irradiation was initiated with DEAP (2,2-diethoxyacetophenone) as the initiator and was shown to be complete after 15 min. At pH 6, polymer was desorbed from the inner membrane surface to form a lamellar structure similar to that of the cellular cytoskeleton, as shown by electron microscopy. In comparison to NIPAM (N-isopropylacrylamide), which was used as a monomer in a recent study (Stauch, O.; Uhlmann, T.; Frohlich, M.; Thomann, R.; El-Badry, M.; Kim, Y.-K.; Schubert, R. Biomacromolecules 2002, 3, 324-32), DMAPMA shows much slower membrane permeation leading to an essential restriction of the formed polymer to the liposomal interior. The DMAPMA-based composite structure stabilizes the lipid membrane against sodium cholate by a factor of 2.5 as compared to plain EPC liposomes. This is discussed in the context of the situation in the liver, where the cytoskeleton probably plays a crucial role in the stabilization of the membrane against high bile salt concentration.

Einsatz von Echinacea-Extrakt bei tragenden und säugenden Sauen

Abstract. Title of the paper: Application of Echinacea-extract in pregnant and suckled sows In an experiment with thirteen sows (echinacea: n = 6; control: n = 7), the influence of Echinacea purpurea treatment of pregnant and suckled sows on immune system, health status, growth performance, and carcass quality of the offspring (echinacea: n = 69; control: n = 79) was investigated. Echinacea was given as liquid feed supplement during the whole pregnant and suckling period of sows in six intervalls (5 days of treatment, followed by 2 weeks of break, respectively). During the treatment time the daily dosage per sow in echinacea-group was 0.125 ml preparation of echinacea extract (incl. solution)/kg body weight. To measure the concentrations of immunoglobulin G (IgG), immunoglobulin A (IgA) and C-reactive protein (CRP) in serum, blood samples were taken by punction of V. cava cranialis (sows and piglets) at different times. The treatment of sows resulted in immunostimulatory effects both in sows and piglets with highest changes in peripartal period. In one day old piglets, the concentrations of IgG, IgA and CRP were significantly increased in echinacea-group (P = 0.0004, P < 0.0001, P = 0.05, respectively). Up to day 70 of age, the rate of therapeutical treatments of piglets from echinacea-treated sows was decreased in tendency (P = 0.08). The growth performance and carcass quality of offspring was not influenced by echinacea treatment of sows.