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Model studies on the mechanism of endotoxin adsorption on flat-sheet microfiltration membrane adsorbers

The adsorption of endotoxin from E.coli O 111:B₄ and bovine serum albumin on membrane adsorbers with the ligands polymyxin B, L-histidine, deoxycholate, poly(L-lysine), poly(ethyleneimine) and diethylaminoethyl was studied under equilibrium and dynamic conditions. Apparent association constants varied between 30 and 30 000 mL/mg for endotoxin, whereas with BSA only approximately 1 mL/mg was found on average. With all ligands a reduction of the removal efficiency was experienced in the presence of BSA, which was used as model protein. Detailed analysis of the influence of BSA on the association constants as well as the equilibrium and dynamic capacities of endotoxin adsorption demonstrated that endotoxin and BSA molecules recognize distinct binding centres on the membrane adsorbers. Competition for binding sites plays a less important role than assumed so far. It is concluded that interactions of endotoxin with protein molecules in solutions are limiting endotoxin clearance from protein solutions. With net-positively charged proteins, electrostatic interactions yield protein-endotoxin complexes. Net-negatively charged proteins attract endotoxin by the mediation of calcium ions that are derived from endotoxin micelles and vesicles. In the latter case, endotoxin clearance can be significantly improved by the addition of EDTA.     

Natürliche Antioxidantien V Antioxidantien und Synergisten aus antarktischem Krill

Natural Antioxidants V: Antioxidants and Synergists of Antarctic Krill Addition of meat of antarctic krill (Euphausia superba Dana) to other food increases their resistance concerning the oxidative decay. It is possible to isolate the antioxidative principle from krill and to separate it into a lipophile and a hydrophile fraction. The lipophile component is found as α-tocopherol, the hydrophile as synergeticly efficient mixture of 13–20 free amino acids.     

Interaction between polymers in dilute solutions of two polymers in a single solvent measured by light scattering and the compatibility of polymers

The intensity of light scattered from dilute solutions of mixtures of two nonidentical polymers in a single solvent was measured. The parameter A₂₄ characterising the thermo-dynamic interaction of two nonidentical polymer molecules in solution was calculated for several systems polymer 2 - polymer 4 - solvent. For chemically strongly different polymers, A₂₄ is independent of molecular weights of the polymers and probably also of solvent. A₂₄ is related to the compatibility of both polymers and decreases contrary to expectation with increasing chemical difference between polymers 2 and 4.     

Chromatin-unstable boar spermatozoa have little chance of reaching oocytes in vivo

In the present study, the prevalence of chromatin instability in the fertilizing-competent sperm population in the porcine oviduct in vivo was examined through qualitative analysis of the chromatin structure status of accessory boar sperm found in in vivo-derived embryos. The binding of chromatin-unstable sperm to oviductal epithelium in vitro was also studied. To examine the sperm chromatin state, a modified fluorescence microscopic sperm chromatin structure assay was used. Among a population of 173 fertile boars, individuals were selected for according to their chromatin status: 25 animals showed more than 5% of chromatin-unstable sperm in their ejaculates, and 7 showed consistently elevated percentages of chromatin-unstable sperm in three successively collected semen samples. A positive correlation was found between incidence of chromatin instability and attached cytoplasmic droplets (r=0.44, P<0.01). Analyses of accessory spermatozoa from in vivo-derived embryos demonstrated that the proportion of chromatin-unstable sperm was significantly (P<0.05) reduced in the population of fertilizing-competent sperm in the oviduct compared with the inseminated sperm. Populations of sperm bound to the oviduct in vitro had significantly (P<0.05) lower percentages of chromatin instability than in the original diluted semen sample. In conclusion, numbers of sperm with unstable chromatin are reduced in the oviductal sperm reservoir, possibly because of associated changes in the plasma membrane that prevent sperm from binding to the oviductal epithelium. We conclude that in vivo the likelihood that sperm with unstable chromatin will reach the egg and fertilize it is low.