Exchange of phosphatidylcholine between small unilamellar liposomes and human plasma high-density lipoprotein involves exclusively the phospholipid in the outer monolayer of the liposomal membrane

By making use of the capacity of phospholipase A₂ to degrade selectively the phospholipid in the outer half of the lipid bilayer of small unilamellar phospholipid/cholesterol vesicles without affecting the retention of a vesicle-encapsulated solute, we demonstrated that the exchange of phosphatidylcholine between such vesicles and human high density lipoprotein involves exclusively the phosphatidylcholine present in the outer monolayer of the vesicle membrane.     

Formic acid and saturated hydrocarbons as alarm pheromones for the ant Formica rufa

Releasers for the most intense, the fast-running, phase of the alarm behaviour were studied in worker ants of the formicine ant Formica rufa. The investigation was performed with a new technique in which the intensity and the duration of the behaviour pattern were measured in an objective and automatic way.Workers of formicine ants eiect a mixture of formic acid and the secretion from Dufour's gland against an enemy. The secretion from this gland in F. rufa consists of a great number of substances, 39 of which have been identified. The dominating substances form a homologous series of aliphatic, saturated hydrocarbons. Some of these hydrocarbons as well as the formic acid are alarm pheromones. The behavioural threshold value for one of these compounds, decane, was lower than 5.10¹³ molecules cm^?3 air. The threshold value for formic acid was estimated to 7.10¹⁵ molecules cm^?3 air. Formic acid and undecane are shown to belong to different reaction groups. The hydrocarbons, on the other hand, seem to affect the same kind of acceptor or receptor.The total intensity and duration of the alarm behaviour released by formic acid and one hydrocarbon are additive if the two substances are combined in a stimulus. A combination of two hydrocarbons and formic acid release a stronger behaviour than one hydrocarbon with formic acid even when the two stimuli contain the same number of molecules. The hydrocarbons have a combined effect and their relative concentrations regulate the intensity and duration of the alarm behaviour.     

H-2-associated specificity of virus-immune cytotoxic T cells fromH-2 mutant and wild-type mice: M523 (H-2K ka ) and M505(H-2K bd ) do,M504 (H-2D da ) and M506(H-2K fa ) do not crossreact with wild-typeH-2K orH-2D

B10.A(3R) (H-2K ^b ) mice infected with lymphocytic choriomeningitis virus (LCMV) or vaccinia virus generate cytotoxic T cells capable of specifically lysing virus-infected macrophage target cells fromH-2K ^b mutant mice M505 (H-2K ^bd ), and vice versa. Similarly, virus-immune B10.A(4R) (H-2K ^k ) T cells specifically lyse infected targets from M523 (H-2K ^ka ), and vice versa. In contrast, virus-specific cytotoxic T cells from neither M504 (H-2D ^da ) and B10.A(5R) (H-2D ^d ) nor M506 (H-2K ^fa ) and B10.M(11R) (H-2K ^f ) mutually crossreact at the cytotoxic effector-cell level. As far as tested, the crossreactivity patterns between wild-type and mutantK orD specificities are identical for LCMV- and vaccinia virus-immune spleen cells. Although this finding is no proof for either the altered self nor the dual recognition concept of T-cell recognition, it may be compatible with the latter model.     

Eine neue Singvogel-Gattung,Cichladusa

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Studien über die Funktion der im Wasser gelösten Nähr substanzen im Stoffwechsel der Wassertiere

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