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G Döring

Publications and source records attributed to G Döring.

At least 127 records · Page 7Linked to original sources
PubMed1981

[Extracellular toxins of Pseudomonas aeruginosa. I. Purification and characterization of two exoproteases (author's transl)].

Alkaline protease (protease I) and a protease with elastase activity (protease II) were isolated from two different strains of Pseudomonas aeruginosa (PA). Proteolytic activity was measured during the early exponential phase of growth and was highest when cultures reached the stationary growth phase. The extracellular character of protease I and II was demonstrated by measuring the intra- and extracellular ATP-concentration. Purification was achieved by precipitation with 65% ammonium sulfate, precipitation with 70% acetone, gelfiltration on Sephadex G-100 and chromatography on DEAE-Sephacel. The purified proteases were characterized. The pH for optimal proteolytic activity of protease I was at pH 9--10, for protease II at pH 8--9. Both enzymes cleaved casein and gelatine, in addition protein II elastin. Enzymatic activity of protease II was inhibited by 10(-3) M EDTA at pH 8.1 to 82%. Inactivation of protease I was not achieved by 10(-2) M EDTA. Molecular weight of protease I was estimated at 57,000, molecular weight of protease II at 39,000. Both enzymes consist of one polypeptide chain. In isoelectric focusing the protease I was separated into two components with pH values of 8.5 and 8.7, while protease II had isoelectric points of pH 6.0 and 6.4. Further characterization of protease I was done with amino acid analysis. Protease I was fairly stable over a pH range of 6--9 at room temperature. The optimal temperature for proteolytic activity was 60 degrees C. The results are discussed in view of proteases of other PA-strains.

Amino Acids↗
PubMed1981

[Extracellular toxins of Pseudomonas aeruginosa. II. Effect of two proteases on human immunoglobulins IgG, IgA and secretory IgA (author's transl)].

Two proteolytic enzymes of Pseudomonas aeruginosa--an alkaline protease and an elastase--were incubated with human myeloma proteins IgG and IgA as well as with secretory IgA at 37 degrees C. Digest mixtures were analyzed after 1, 5, 12, 24, 48 and 72 h by SDS-polyacrylamide gel electrophoresis after reduction by 2-mercaptoethanol. Under conditions which resulted in cleavage of all three immunoglobulins by the elastase in the hinge-region, the alkaline protease cleaved only IgA. It was suggested that proteases of PA interfere with the immune-system of the host by cleavage of immunoglobulins. Elastase-positive PA strains should be more virulent compared with PA strains which produce only alkaline protease or are protease-negative at all.

Exopeptidases↗
PubMed1980

[What type of contraceptive method can the physician recommend?].

Contraceptives should be reliable, innocuous and compatible. With reference to their reliability (Pearl-index) they can be devided into four groups. Only the oral contraceptives can be classified as "reliable". The risk of women over 40 for myocardial infarction is only barely raised by the pill according to new data. "Relatively reliable" are intrauterine devices, the mini-pill, the temperature method and the foam ovula containing 4 p-Nonyphenoxypolyethylenglycol. Failures are ten times as frequent as with the oral contraceptives. Adnexitis caused by intrauterine devices ist seven times more frequent in nulliparae than in the average female population. Among oral contraceptives, the mini-pill is the only one without appreciable side-effects, risks, or contraindications. Grade three preventives ("medium reliability") should be used for child spacing. The fourth group of unreliable methods comprises the Knaus-Ogino method, coitus interruptus and the long-established chemical preventives.

Contraception↗
PubMed1979

[Animal experiments on the detection of an exposure to "chemical mace" (author's transl)].

To answer the question whether a negative result of gas chromatographic blood analysis for components of chemical mace proves that no or at most only slight tear gas exposure can have occurred, animal experiments were carried out. In the blood of 10 guinea pigs, which were exposed to the contents of chemical mace for 1--6 h, the solvants 1,1,2-trichloro-1,2,2-trifluorethane (freon 113) and 1,1,1-trichloroethane could easily be detected--even 23 h after the end of exposure or after a storage of the blood samples for 18 weeks--whereas the lacrimator chloracetophenone (CN) could not be found at all. In vitro experiments showed that CN relatively quickly reacts with components of blood. Therefore, blood samples should be analyzed for CN after withdrawal as soon as possible. In case of inhalation of the contents of chemical mace, i.e., after the comparatively mildest form of CN application, most probably no traces of the lacrimator at all can pass into the blood due to the quick reaction of CN with proteins of the respiratory surface of the lung.

Animals↗
PubMed1979

Metabolism of isomeric N-methyl-N-nitroso-(methylphenyl)-methylamines.

Isomeric N-methyl-N-nitroso-(2-, 3-, and 4-methylphenyl)-methylamines (2a, 2b and 2c, Fig. 1.) were metabolized in rats to the corresponding 2-, 3- and 4-(N-methyl-N-nitroso-aminomethyl)-benzoic acids (4-MNAB) (3a, 3b and 3c). The structures of 3b and 2c were established by synthesis and confirmed by spectroscopic evidence. Metabolic formation of 3a, 3b and 3c was determined by HPLC analysis and the time-course of 3c excretion was established. Oral intubation of the acid 3c resulted in almost quantitative excretion of this metabolite in 24 h urine thus indicating rapid detoxication. Toxicity and carcinogenicity of the isomeric 2a, 2b and 2c were compared with those of the parent N-methyl-N-nitroso-benzylamine (MNBA).

Animals↗
PubMed1976

Studies on the nature of the inhibitory effect of trypsin on the photosynthetic electron transport of system II in spinach chloroplasts.

The effect of trypsin on the photosynthetic electron transport of spinach chloroplasts has been investigated by measurements of the flash-induced absorption changes, indicating chlorophyll a1 at 703 nm, chlorophyll aII at 690 nm and at 515 nm via electrochromism the electrical potential gradient across the thylakoid membrane, respectively, and of the fluorescence induction caused by moderate actinic light. It was found: (1) In the presence of benzyl viologen as electron acceptor and with water as natural electron donor trypsin, incubation leads to a complete suppression of the absorption changes of the electrochromic effect and of chlorophyll aI and chlorophyll aII. (2) Addition of System I electron donors (N-methylphenazonium sulfate plus ascorbate or 2,6-dichlorophenolindphenol plus ascorbate) fully restores the chlorophyll aI photoreaction, whereas the initial amplitude of the electrochromic absorption change at 515 nm amounts about 50% of the control value without trypsin. The chlorophyll aII inhibition remains uneffected by System I electron donors. (3) System II electron donors (benzohydroquinone plus ascorbate or TPB) are unable to overcome the inhibition of electron transport by trypsin. (4) The fluorescence induction curve in 3-(3,4-dichlorophenyl)-1,1-dimethyl-urea-blocked chloroplasts is modified by trypsin. The level of maximal fluorescence is remarkably decreased, whereas the initial fluorescence remains constant. The rise in kinetics is slightly decelerated. From these results, it is concluded that in the linear electron transport from water to benzyl viologen, mild trypsin treatment specifically attacks System II at a site very close to the reaction center, either on the oxidizing or on the reducing side. The reaction center of System II itself is relatively stable against trypsin. Arguments are presented which argue in favor of the trypsin attack being primarily directed at the reducing side of System II.

2,6-Dichloroindophenol↗
PubMed1976

[Propane-diol-(1.3) fatty acid esters as metabolites of postmortal triglyceride catabolism (author's transl)].

The investigation of 72 samples of human subcutaneous fat tissue stored in closed small bottles at room temperature showed that every third sample decomposed with the formation of unknown metabolites. The presence of these compounds could already be recognized in the crude lipid extracts by characteristic 1H-NMR signals, increasing in intensity with time of storage. After isolation, the unknown metabolites could be identified as di- or mono fatty acid esters of propane-diol-(1.3). Thus, the known scheme of postmortal breakdown of triglycerides is to be supplemented by a further remarkable pathway.

Adipose Tissue↗
PubMed1975

Further results on the photoactive chlorophyll aII in photosynthesis.

1. The flash-induced difference spectra of chlorophyll aII in untreated and in heat-treated spinach chloroplasts are presented. 2. Heat-treatment leads to an increase of the half-life of the chlorophyll aII absorbance changes. After the addition of hydroquinone plus sodium ascorbate the half-life of the chlorophyll aII reaction returns nearly to the value in untreated chloroplasts. 3. In digitonin-treated chloroplasts, or in the presence of histone, the chlorophyll aII activity is low when the electron acceptor is benzylviologen and high when ferricyanide is used. 4. The half-life of the chlorophyll aII reaction depends on the temperature of the reaction mixture. The activation energy of the chlorophyll aII reaction is about 7.5 kcal/mol. 5. From the experimental results we conclude that in heat-treated (and in Tris-washed and aged) chloroplasts the linear electron flow in Photosystem II is replaced by a cyclic one, which is sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

Chlorophyll↗