Effect of C2 ceramide on the inositol phospholipid metabolism (uptake of 32P, 3H-serine and 3H-palmitic acid) and apoptosis-related morphological changes in Tetrahymena.

Sphingomyelin metabolites have significant role in the regulation of many life processes of mammalian cells. In the present experiments the influence of phospholipid turnover and apoptosis related morphologic signs by one of this metabolite, C2 ceramide was studied, and compared to the control, untreated cells, in the unicellular Tetrahymena. The incorporation of phospholipid head group components (serine, phosphorus) show a clear time-dependence; while the incorporation of fatty acid component (palmitic acid) is very fast: no significant alterations were found between 5- and 60-min incubations. C2 ceramide treatment didn't alter 3H-palmitic acid incorporation into phospholipids, however 3H-serine incorporation was mainly inhibited. The amount of total incorporated 32P was also decreased, on the other hand the lover concentration C2 ceramide (10 microM) elevated the synthesis of inositol phospholipids. The higher concentration of C2 ceramide (50 microM) had inhibitory effect on the synthesis of each phospholipids examined. This means that in the presence of the C2 ceramide the synthesis, recovery and turnover of phospholipids, participating in signal transduction, are altered. However these observations were based the uptake of labeled phospholipid precursors, which gives information on the dynamics of the process, without using lipid mass measurements. C2 ceramide also caused the rounding off the cells, DNA degradation and nuclear condensation. These latter observations point to morphological signs of apoptosis. The results call attention to the role of sphingomyelin metabolites on signalization of unicellulars, to the cross-talk between the inositol phospholipids and sphingomyelin metabolites, and the role of these molecules in the apoptotic processes at a low evolutionary level.

[Effect of ciprofloxacin therapy in duration of bacterial excretion in acute salmonella gastroenteritis]. / Einfluss einer Ciprofloxacin-Therapie auf die Ausscheidedauer bei akuter Salmonellen-Gastroenteritis.

In view of the increasing incidence of non-typhoid salmonellosis, the effect of early treatment with ciprofloxacin on the permanent elimination of salmonella was evaluated. In a prospective study, 14 patients with non-typhoid salmonellosis were treated with 2 x 500 mg/d ciprofloxacin for 10 days within 5 days of onset of symptoms. Relapse occurred in 4/14 (29%) patients 2-3 weeks after termination of therapy. Using sero- and ribotyping, relapse was confirmed and reinfection ruled out in 4/4 patients. Furthermore, ribotyping suggested double infection in one patient. Development of resistance to ciprofloxacin was not observed. We conclude that the use of antimicrobial chemotherapy to treat non-institutional salmonellosis in immunocompetent patients cannot generally be recommended but must be considered carefully in each case. Indications for ciprofloxacin therapy in the treatment of non-typhoid salmonellosis are discussed.

Absolute configuration and local anaesthetic activity of cis and trans 2-dimethylaminomethyl-cyclohexyl benzoates.

All the four stereoisomers of 2-dimethylaminomethyl-cyclohexyl benzoate (enantiomers of 4 and 5) were prepared in optically pure state and their absolute configurations determined by chiroptical methods and genetic correlations. The configurational assignments obtained by the two independent methods were in full agreement and the absolute configuration of the four stereoisomers are (+)-(1S,2S)-4, (-)-(1R,2R)-4, (+)-(1S,2R)-5, and (-)-(1R,2S)-5. The local anaesthetic activity of the four compounds were also determined.

The asymmetric transmembrane distribution of phosphatidylethanolamine, phosphatidylserine, and fatty acids of the bovine retinal rod outer segment disk membrane.

The transmembrane distribution of the major aminophospholipids in the bovine retinal rod outer segment disk membrane, phosphatidylethanolamine and phosphatidylserine, was determined using a novel pair of permeable and impermeable covalent modification reagents. The values for the percentages of phosphatidylethanolamine and phosphatidylserine in the outer monolayer were calculated from a simple expression which takes into account the leakage of impermeable reagent into the disk lumen as monitored by the extent of labeling of lysine entrapped in the lumen. We infer from our results that at least 73 to 87% of the disk phosphatidylethanolamine and 77 to 88% of the disk phosphatidylserine are in the outer disk membrane monolayer. The fatty acid composition of the inner aminophospholipids is slightly more saturated than the outer aminophospholipids. Calculations using the lateral surface areas occupied by the disk membrane lipids suggest that 65 to 100% of the disk phosphatidylcholine is on the inner membrane surface. Since the disk phosphatidylcholine is also somewhat more saturated than the phosphatidylethanolamine and phosphatidylserine of the outer monolayer, the total inner membrane monolayer fatty acid composition is more saturated than that of the outer monolayer fatty acid composition.

Covalent modification of rhodopsin with imidoesters: evidence for transmembrane arragnement of rhodopsin in rod outer segment disk membranes.

The transmembrane disposition of the visual pigment rhodopsin was studied by the covalent labeling of protein amino groups with membrane-permeable and -impermeable imidoesters. A new, highly reactive permeable reagent, 2-(methylsulfonyl)ethyl acetimidate (SAI) was developed for this purpose. The permeabilities of both this compound and the "impermeable" reagent isethionyl acetimidate (IAI) across the rod outer segment disk membrane were directly measured. Our results indicate that rhodopsin contains three classes of amino groups. One class (35--55% of the total) reacts rapidly with the membrane-impermeable reagent and is presumably exposed on the outside surface of the membrane. A second class (35--55% of the total) is located on the internal surface of the disk since its rate of reaction is dependent on the relative permeabilities of the labeling reagents. The remaining 10% of the rhodopsin amino groups are inaccessible to either type of imidate and are largely accounted for by the single lysine residue which specifically binds the chromophore retinal. These findings, taken together with evidence from freeze--fracture electron microscopy, imply that rhodopsin is a transmembrane protein.