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Biomedical subjects

U Winkler

Publications and source records attributed to U Winkler.

At least 91 records · Page 5Linked to original sources
PubMed1982

Glycogen and various other polysaccharides stimulate the formation of exolipase by Pseudomonas aeruginosa.

Glycogen enhances the formation of exolipase by Pseudomonas aeruginosa ATCC 9027 although the cells cannot utilize it as sole carbon and energy source. Glycogen is unable to influence exolipase activities in conditioned media after removal of the cells. Treatment of cells with glycogen does not promote overall protein synthesis but inhibitors of protein synthesis (e.g., rifampicin and chloramphenicol) prevent the glycogen effect, suggesting that specific de novo protein synthesis is required. In addition to glycogen, 5 other polysaccharides (among 13 tested) were found to have exolipase-enhancing ability. The results are discussed with regard to the detachment hypothesis of U.K. Winkler and M. Stuckmann (1979. J. Bacteriol. 138: 663-670). According to this hypothesis polysaccharides are assumed to dislocate cell-bound lipase to the medium via specific interactions with the bacterial cell surface.

Anti-Bacterial Agents↗
PubMed1979

Relaxed mutants of Serratia marcescens SM-6. Biochemical traits and relevance of the rel+ allele for the formation of exoenzymes.

Serratia marcescens SM-6 when starved for a required amino acid stops synthesizing protein and RNA and accumulates two nucleotides which co-chromatograph with ppGpp and pppGpp. These features are characteristic of bacterial strains with stringent RNA control (rel+). Two independent mutants were isolated which resemble relaxed (relA) mutants of Escherichia coli; they continue to synthesize RNA and accumulate neither ppGpp nor pppGpp when deprived of the required amino acid. The extracellular enzyme activities (nuclease, protease, lipase) of the relaxed mutants are about the same as those of the parental stringent strain when studied under standard growth conditions. Exoenzyme-deficient (nuc;prt) and exoenzyme-hyperproducing (nucsu) mutants were isolated from both stringent and relaxed strains of S. marcencens SM-6 and no change of the cellular ability to form ppGpp and pppGpp could be observed. From these results it appears that the formation of exoenzymes of S. marcescens SM-6 is independent of stringent/relaxed RNA control.

Alleles↗
PubMed1978

Pleiotropic consequences of mutations towards antibiotic-hypersensitivity in Serratia marcescens.

Various mutants (oxas) were isolated from Serratia marcescens SM-6 by selecting for hypersensitivity towards oxacillin. All mutants found are highly pleiotropic and able to yield spontaneous revertants which behave like the wild-type. Mutant W 1421 mostly studied shows the following phenotypic properties not found in the wild-type: (1) The growth is hypersensitive to various antibiotics, detergents and dyes which differ remarkably in their chemical structure and antibacterial action-mechanism, (2) the cells can be easily solubilized by 0;05% Sodium-dodecyl-sulfate, (3) the cells allow the adsorption of the rough-mutant specific Salmonella phage 6SR; (4) strong cellular binding of crystal violet, (5) agglutination of the cells in 0.3% auramin solution and (6) reduced formation of red pigment. Strain W 1421 is assumed to be a lipopolysaccharide-defective mutant. The outer membrane of mutant W 1421 analyzed by Sodium-dodecylsulfate-polyacrylamide gel electrophoresis possesses a single protein less than that of the wild-type. Mutant W 1421 is further characterized by its low exolipase activity; exoprotease and exonuclease activities are as in the wild-type. This specific exoenzyme deficiency can be overcome either by backmutation to oxacillin-resistance or by growing mutant W 1421 in a medium supplemented with certain non-metabolizable polysaccharides, e.g. glycogen or pectin B. Both polysaccharides increase the exolipase activity of the wild-type too.

Anti-Bacterial Agents↗
PubMed1976

Experimental analysis of developing hemopoiesis in fetal bone marrow.

1. We have used fetal rats to study the following aspects of the development of hemopoiesis: (a) content of hemopoietic stem cells in fetal bone marrow, liver, and peripheral blood and (b) origin of hemopietic cells in the developing mammalian bone marrow. 2. In the studies we utilized the diffusion chamber technique to study the content of stem cells committed to granulopoiesis. The number of myelopoietic stem cells in liver peripheral blood and in "bone marrow" of 18-day-old rats is nearly identical. Since in "bone marrow" a considerable number of peripheral blood cells are present in the vessels at that time, whereas extravascular cells consist only of mesenchymal cells, one might assume that these peripheral blood cells give rise to granulocytic precursors in the cultures. Morphologically these cells are "blast" cells and lymphocytes. 3. Based on cell labeling indices of radioautograms, derived from continuous infusion of pregnant rats with [3H]thymidine, it could be shown that in the perichondral area mesenchymal cells of the fetus and newborn have a slow rate of DNA turnover whereas "bone marrow" cells are in an active state of profileration. 4. In further support of this it was also shown that injections of hydroxyurea (an agent which destroys cells in DNA synthesis) has vitrually no effect on perichondral mesenchymal cells whereas "bone marrow" cells were completely blocked in their ability to support myelopoietic differentiation in the diffusion chamber implants. 5. The conclusions would therefore be that (a) local perichondral cells, i.e., mesenchymal cells, do not contribute to marrow hemopoiesis, (b) matrix cells of the developing bone marrow cannot reconstitute hemopoiesis, and (c) hemopoietic bone marrow cells develop from migrating peripheral "stem cells", one of the sources being the liver.

Animals↗
PubMed1976

[Comparative clinical and experimental studies of various denture cleansers. 2. Testing of antimicrobial efficiency].

Agar diffusion plate tests were performed on five strains of micro-organisms to characterize the disinfecting properties of nine denture cleaners. Furthermore, the liberation of oxygen was determined as a function of time, and the course of pH variation of the various cleaning solutions was studied. The highest oxygen concentrations and the best antimicrobic activities were achieved by the preparations Eladent G and T.

Bacteria↗
PubMed1975

Mutants of Serratia marcescens lacking cyclic nucleotide phosphodiesterase activity and requiring cyclic 3',5'-AMP for the utilization of various carbohydrates.

Adenine requiring mutants of Serratia marcescens SM-6-F'lac+ have been found to grow well in minimal-glucose medium solely supplemented with cAMP. From one of these ade strains double mutants (called ade cpd) were isolated which could no longer utilize cAMP but which still grew on 5'AMP. Dialyzed cell extracts (soluble fraction) of the double mutants, assayed for cAMP phosphodiesterase, were unable to hydrolyze cAMP whereas cell extracts of the parental strains yielded 5'AMP at a rate of 1.6-2.0 mumoles min-1 mg-1 protein. The loss of the phosphodiesterase activity in S. marcescens cpd W 1181 did not cause an accumulation of large amounts of cAMP as was found for the diesterase-negative mutant AB257pc-1 of Escherichia coli. The induced synthesis of beta-galactosidase in mutant cpd W 1181 showed about the same sensitivity to transient and permanent catabolite (glucose) repression as the corresponding cpd+ strain. Starting from S. marcescens cpd W 1182 three independent double mutants (called cpd cya) were isolated which required exogenous cAMP for utilizing various carbohydrates as carbon source, for motility and for the formation of extracellular lipase and the red pigment prodigiosine. The intracellular concentration of cAMP in these mutants, grown in nutrient broth, was 40-60% of that of the parental strain which is about 4 x 10(-4) M. However, the adenylate cyclase in cell extracts of the mutants W 1237 and W 1270 was like that of the corresponding cya+ strain (about 2 x 10(-2) mumoles min-1 mg-1 protein).

3',5'-Cyclic-AMP Phosphodiesterases↗